i 1 i i i i i 1 Marine Biological Laboratory Library Woods Hole, Mass. Presented by Dr. Wm. Amberson 1 i A I I I I I I J l! m zr tr r-R D O CD m CD HUMAN PHYSIOLOGY MACMILLAN AND CO., LIMITED LONDON BOMBAY CALCUTTA MELBOURNE THE MACMILLAN COMPANY NEW YORK BOSTON CHICAGO ATLANTA SAN FRANCISCO THE MACMILLAN CO. OF CANADA, LTD. TORONTO HUMAN PHYSIOLOGT 7 1 V. BY PROFESSOR LUIGI LUCIANI DIRECTOR OF THE PHYSIOLOGICAL INSTITUTE OF THE ROYAL UNIVERSITY OF ROME TRANSLATED BY FRANCES A. WELBY EDITED BY DR. M. CAMIS INSTITUTE OF PHYSIOLOGY, UNIVERSITY OF PISA WITH A PREFACE BY J. N. LANGLEY, F.R.S. PROFESSOR OF PHYSIOLOGY IN THE UNIVERSITY OP CAMBRIDGE IN FOUR VOLUMES VOL. I. CIRCULATION AND RESPIRATION MACMILLAN AND CO., LIMITED ST. MARTIN'S STREET, LONDON 1911 PREFACE " GOOD wine needs no bush," but it will perhaps not be an in- fringement of this maxim to introduce, in a few words, Professor Luciani's excellent Text-Book of Physiology to the English-reading public. The Italian Text-book is now in its third edition, the final pages being in the Press. One or other of the earlier editions has been translated into French, German, and Russian, and it is a matter for surprise that we have had to wait so long for an English version. In the making of physiological text -books, we are at the parting of the ways. The physiologists of the past generation were brought up to know with familiarity all that had been recently done in physiological research, whether in vertebrates or invertebrates, in animals or in plants. The facts were not so numerous that they could not be stored in the memory without cumbering the judgment, and Physiologists could in some sort be first-hand authorities on all branches of the subject. That condition has been gradually passing away, and it is hardly possible for any one who is not of the old school to write an advanced text-book covering the whole ground of Physiology. Thus the text-book of single authorship is giving way to the text-book of multiple authorship. The latter, whatever its merits, has not the unity of view and the sense of proportion which belong to the former qualities very important in a book intended Fur students. Professor Luciani's book, whilst describing phenomena with considerable detail, treats lucidly the broad principles to be deduced from them. It stands midway between the text-book which confines itself to summing up the results of physiological investigation, and that which gives also a minute historical account of the progress of investigation. It deals with the main vi PHYSIOLOGY outlines of the history of each branch of the subject, but does not allow this to interfere with the even flow of narration. It is natural that writers of Text-books should make frequent reference to the work that has been done by their own country- men. Italian work is less widely known than it deserves, and one of the advantages of this book for English-speaking folk is that Italian workers receive their meed of notice. It will, how- ever, be a shock to many English readers to find that Professor Luciani allots the discovery of the systemic circulation of the blood to his countryman, Cesalpiuus. That the circulation of the blood was described and demonstrated by Harvey, no one doubts. That there were a number of forerunners of Harvey who under- stood this or that important fact connected with the circulation is equally undoubted. In considering the place to be assigned to each of those who helped to solve the problem, two separate questions arise. First, How far are the facts and views original and not obtained from unacknowledged sources I and secondly, What was the exact degree of understanding of the subject possessed by each writer ? It may seem that the former question only would be difficult to solve. In fact, the difficulty of the latter is no less, or at any rate differences of opinion with regard to it have not been less ardent ; and so we find that whilst most authorities regard Cesalpiuus as having but imperfectly compre- hended the systemic circulation, and to have seen it " darkly through Galenical glasses," some, as Professor Luciani, consider that his comprehension was whole and without flaw. Finally, it may be noted that the Editor, Dr. Camis, has added at the end of each chapter a selected list of English-written Monographs and Papers, and thus has put the student who knows no other language than English in the way of obtaining a fuller knowledge of any branch of Physiology in which he may be interested. J. ]S T . LANGLEY. CAMBRIDGE, Jan. 1911. TRANSLATOR'S NOTE I BEG to offer rny sincere thanks to Dr. Aders-Plimmer for his kind help in the translation of the chemical section of this volume : and to Mr. W. L. Symes for assistance in many other technical difficulties. FKANCES A. WELBY. LONDON, October 1910. VII CONTENTS PAGE INTEODUCTION . . ... 1 1. Threefold division of biological science. 2. Special objects of physiology. 3. Materialism, neo-vitalism, Ostvvald's energetic monism, Mach's psychical monism, pragmatic pluralism. 4. Physiology of the cell ; general and comparative physiology ; human physiology. Bibliography. CHAPTER I LIVING MATTER : ITS CHEMICAL AND PHYSICAL BASIS . 1 1 1. The cell-theory. 2. Morphology of the cell. 3. Structure of protoplasm. 4. Structure of nucleus. 5. Chemical elements of the cell. 6. Protein basis of living matter. 7. Classification of proteins. 8. Chemical constitution of proteins. 9. Enzymes or ferments. 10. Classification. 11. Other nitrogenous organic substances, fats, carbo- hydrates or saccharides, inorganic substances. 12. Chemical structure of living matter. Bibliography. CHAPTER II LIVING MATTER : ITS FUNDAMENTAL PROPERTIES . . .42 1. Vital metabolism, and phenomena of nutrition and repro- duction. 2. Vital metabolism and phenomena of excitability and sensibility. 3. Laws of stability and variability of living species. Critical examination of Theory of Evolution ; Darwinism, and Neo- Lamarckism. 4. Evolutionary theories of Nageli, Weismann, De Vries. 5. Distinctive characters -of plants and animals : () Doctrine of Linnaeus ; (b) doctrine of Cuvier ; (c) doctrine of J. R. Mayer, Dumas, Liebig. 6. Different forms of plant and animal metabolism : (u) Nitri- fying bacteria ; (J) green plants ; (<) a-chlorophyllous plants ; (d) herbivorous and carnivorous plants. Bibliography. ix PHYSIOLOGY CHAPTER III PAGE LIVING MATTEU : CONDITIONS BY WHICH IT is DETERMINED 64 1. Nutrition the necessary external condition of vital metabolism. Phenomena of inanition. 2. Importance of water. Latent life and anabiosis. 3. Importance of oxygen. Aerobic and anaerobic life. 4. External temperature indispensable to life. 5. Total pressure of air and water, and partial pressure of oxygen and carbonic acid. 6. Ex- ternal stimuli. 7. Chemical stimuli. Chemotaxis. 8. Mechanical stimuli. Barotaxis. 9. Thermal stimuli : thermotaxis. 10. Photic stimuli. Phototaxis and Heliotaxis. 11. Electrical stimuli. Galvano- taxis. 12. The various biological zones of ocean life (I'liniUnu}. 13. Internal conditions and stimuli of metabolism. Theory of automatism. 14. Hypotheses to explain the intimate mechanism of living matter. Bibliography. CHAPTER IV THE BLOOD : FORMED CONSTITUENTS . . . .91 1. Arrangement of human physiology, and classification of functions. 2. Importance of the blood as centre of the vegetative system and agent of general metabolism. 3. Historical development of haematology. 4. General physico-chemical characters of the blood. 5. Estimation of total quantity. 6. Physical and morphological characters of erythro- cytes, and estimation of their relative quantity. 7. Chemical compo- sition. Properties of haemoglobin and its derivatives. 8. Character, composition, and physiological properties of leucocytes. 9. Blood platelets, and elementary granulation of the blood. Bibliography. CHAPTER V THE BLOOD: PLASMA . ... 123 1. Different methods for separation of blood plasma from corpuscles. 2. Histogenic substances or proteins of plasma : fibrinogen, serum globulin, serum albumin, sero - mucoid. 3. Nitrogenous histolytic products of plasma. 4. Fatty substances. Carbohydrates and their derivatives. 5. Inorganic substances. Blood gases. 6. Theory of Coagulation : () Conditions of blood coagulation ; (b) disintegration of corpuscles as cause of coagulation ; (c) fibrinogen as fibrin generator ; (d) analogies between blood coagulation and curdling of milk ; (c) im- portance of time in coagulation ; (/) thrombin and nucleins as coagu- lating substances ; (. Condition of the lungs and other viscera within tlir thorax; passive movements due to variations in the negative thoracic pressure. 4. The thorneii- cavity ; changes of form and dimensions with inspiratory and expiratory movements. 5. Muscular mechanism of inspiratory and expiratory movements. 6. Normal and furred respiration. 7. Accessory or con- comitant respirator}' movements. 8. Ventilation or renewal of pul- monary air (spirometry), and respiratory pressure in the air-passages (pneumatometry). 9. Respiratory displacement of the lungs, and acoustic phenomena of percussion and auscultation. 10. Respiratory variations of intrathoracic and mtra-abdominal pressure. 11. Respira- tory variations of pressure in the vena cava. 12. Respiratory variations of aortic pressure. 13. Effect of respiratory mechanics on the circula- tion of the blood. 14. Special forms of respiratory movements. Bibliography. CHAPTER XIII THE NERVOUS CONTROL OF RESPIRATORY RHYTHM . 440 1. Motor nerves to respiratory muscles and smooth muscle cells of bronchi. 2. Bulbar respiratory centres and their localisation. 3. Spinal respiratory centres. 4. Cerebral respiratory centres. 5. Each of these centres results from the association of an iuspiratory and an expiratory centre, which function rhythmically and alternately. 6. Automatic regulation of normal respiratory rhythm, by afferent pulmonary film of vagus. 7. Influence exerted on respiratory rhythm vin the cerebral tracts and sensory nerves in general. 8. Phenomena consequent on the separation of the bulb from the brain and spinal cord. 9. Dyspnoea and its different forms. 1Q. Eupnoea or normal quiet respiration. 11. Experimental apnoea from artificial respiration with the bellows. 12. Foetal apnoea, and the analogous forms of experimental apnoea that can be produced in the adult. 13. Voluntary, as compared with experimental apnoea. 14. Apnoea produced by continuous ventilation in birds. 15. Periodic respiration, or Cheyne- Stokes phenomenon. 16. Physiological theory of respiratory rhythm. Bibliography. CHAPTER XIV THE LYMPH, AND INTERCHANGES BETWEEN THE BLOOD AND THE TISSUES 505 1. Structure of lymphatic vascular system, lymph spaces, sinu-c-. and cavities. 2. Origin ; physical, morphological and chemical charac- teristics ; qualitative and quantitative variations of lymph. 3. Lymph- atic circulation, and the various mechanical factors by which it is xiv PHYSIOLOGY determined. 1. Formation of lymph from the blood capillaries, and the so-called lymphagognes. f>. Secretory theory of Eeidenhain, and 1 r,i nsiidation theory of Cohnheim. (i. Formation and modification of lymph by thr tissues. 7. Lymphoid tissue, follicles and lymphatic glands. 8. Bone marrow. 9. The i hymns. 10. The spleen. Bibliography. INDEX OF SUBJECTS . .561 INDEX OF AUTHORS 573 INTRODUCTION 1. Threefold division of biological science. 2. Special objects of physiology. 3. Materialism, neo- vitalism, Ostwald's energetic monism, Mach's psychical monism, pragmatic pluralism. 4. Physiology of the cell ; general and comparative physiology ; human physiology. Bibliography. THE remarkable development of Physiology during the nine- teenth century justifies us in regarding it as one of the most modern sciences ; yet its origin is very ancient, and may be traced back to the first flashes of philosophic thought. Through- out the classical world, however, with few exceptions, the term Physiology (according to its etymological signification) connotes the philosophic study of Nature in general, i.e. it includes the phenomena, not merely of living nature, but of inanimate nature as well. During the Middle Ages, again, until the Renaissance, the Science of Life is confounded with Philosophy, with Natural History, with Medicine in general, and in particular with Anatomy. In the second half of the eighteenth century the immense progress made in the vast field of Natural History (so-called) involved a corresponding division of labour. Intimate relations obtain between mineralogy, geology, and physical geography. These are complementary and reciprocal subjects, which are all included among the inorganic natural sciences. Most intimate, too, are the links connecting botany and zoology : " Between plants and animals," as was happily said by Buffon, " there are more common properties than real differences." Between dead and living nature, however, the gap is far wider, the differences more essential, and the study of the one may be undertaken independent of the other. At the commencement of the last century two eminent natural- ists, Lamarck in France, and Treviranus in Germany, created the word Biology, and applied it in the first instance to designate the complex of closely related sciences which covers the phenomena observed in living beings in general, i.e. in plants, animals, and man. VOL. I 1 B PHYSIOLOGY But if Biology is to include the complete study of life in all its manifestations, it represents a h'eld too vast to admit of comprehension by any single mind in all its details. Hence the necessity arises for a further division of labour. I. If at any given moment of its existence we set out to consider the mode of life and action of any living being, we can at once distinguish the morphological characteristics, depending on anatomical and histological structure, from the functional or physiological features, which are dependent on its cytological, physical, and chemical constitution. If in living beings we consider the development, the perpetual becoming, in other words the morphological and physiological changes they undergo from beginning to end of their existence, we have the story of Evolution, which enables us to a certain point, both for the indi- vidual and the species, to follow the different phases of development as these fulfil themselves according to the great laws of heredity and variation. The complete study of life, to which the term Biology has thus been applied, is appropriately divided into three branches : (a) Morphology, which covers the forms of living beings, i.e. the cellular elements from which the tissues are built up, the connections of the tissues whence the organs develop, the structure of the organs and systems. (6) Physiology, which covers the functions or activities of living beings, and the various cytological, physical, and chemical factors from which these arise : in other words, the storage and dispersal of the energies of which organisms are the seat, and the phenomena or external manifestations by which they are revealed to us. (c) Biogenesis, i.e. the story of evolution, morphological as well as functional, whether ontogenetic, for the individual, or phylo- genetic, for the race. The intimate connections of these three great branches of biological science are obvious. Since organic form is the necessary matrix of function, the study of Physiology perforce includes that of Morphology, or Anatomy as the latter is commonly but loosely termed. These two branches are really offshoots of the same trunk, inasmuch as they constituted in bygone times a single science professed by a single teacher, when the (vastly pre- dominating) study of the morphological signs of life was identified in various ways with that of its physiological properties. But as the study of form has methods of research and problems which are separate and quite distinct from those relating to function, anatomy has gradually detached itself from physiology, pursuing its own independent development. The History of Evolution or Biogenesis, again, which covers a vast field of researches in em- bryology, comparative anatomy, and palaeontology, is evidently INTEODUCTION 3 an offshoot from the common trunk of Morphology and Physiology. In so far as it studies the development of forms it is intimately related to morphology ; inasmuch as it investigates the develop- ment of functions it is united by the closest bonds with physiology. This threefold development of biology rests on no profound scientific postulate, but merely arises from the convenience of a division of labour, whether in fulfilment of a didactic necessity or in order more rapidly to approach the ideal of a comprehensive know- ledge of living phenomena. We may reasonably anticipate that in proportion as the task assigned to each department approaches its completion, and the corresponding methods of investigation are exhausted, the relations will become more intimate, and the intercourse between the workers in the three several fields more frequent, till finally the great Science of Life, completed by all the achievements of morphology, physiology, psychology, and natural science, is reconstituted in its initial unity, as was predicted by Lazzaro Spallanzani and Johannes M tiller. Of late years the special province of Physiology has become so vast that a considerable area of it is now set apart under the name of Chemical Physiology, and it may seem as though we were still very far from the synthetic reconstitution of Biology as a unitary and well-organised science an ideal image of the living organism. Owing, however, to the aforesaid division of labour, or to the undeniable exhaustion of certain superannuated methods in other directions, General or Comparative Physiology, an important department which was too much neglected in the past, has been developed and perfected ; this comprises the collec- tive study of elementary organisms, in which Cytology and Proto- Morphology present to morphologists and physiologists a common field of research. II. In the study of the living organism, the physiologist sets himself three main tasks : to define, to localise, and to interpret the phenomena of life. He aims at (a) Definition of vital phenomena : by describing them exactly, forming, if possible, a graphic image that shall be accurate, not merely in its outlines, but also in its minutest details. (&) Localisation of the different vital phenomena in the several substrata : by determining the specific energies developed by the various elements, tissues, organs, and systems of which the body is composed. (c) Explanation or interpretation of vital phenomena : by in- quiry into their genesis and inner mechanism, investigation of the external or internal conditions on which they depend, deter- mination of the qualitative and quantitative changes they undergo in the play of the said conditions. These three tasks represent three different grades of physiological science. The first is purely descriptive ; the second, descriptive 4 PHYSIOLOGY and experimental ; the third, descriptive, experimental, and speculative. For the first, direct or indirect observation, i.e. the exact perception of vital phenomena, suffices whether by the normal use of the senses only or by the help of instruments designed to reinforce them. For the second, observation is not enough, experiment also is required, i.e. premeditated observation, in which the external and internal conditions of the living phenomena can be varied. In the third, besides observation and experiment, an energetic criticism is imperative, i.e. the logical elaboration by the physiologist of the collected analytical data, in order to interpret and synthetise them. This, in the majority of cases, resolves itself into the arrangement of vital facts in order of co-existence and succession, or of co-ordination and sub- ordination. In the first grade of physiological science we have an accumu- lation of loose facts, more or less unorganised, but adapted to call up a picture of the various and manifold energies of which the living organism is the seat. In the second, we arrive at an ordering and systematisation of the said energies, which enables us more or less clearly to conceive what Galen called the " iisus partium" i.e. the topography of the vital functions. The third aims at harmonising the same energies, in order, by our knowledge of the influences exerted by each element or organ upon 'the other elements or organs of which the body consists, to form an idea as to how that individual unity is built up, which is revealed to us subjectively as the ego, objectively as the complete harmony of functions that characterises the state of perfect health. The first and second' grades of physiological science have a positive, immanent value, which time can only develop and per- fect, while the third has seldom more than a hypothetical value, which is for the most part temporary, and therefore varies with time. It follows that facts, if well observed, and experimental data well harvested, are and will for ever be true in the progress of science, while the interpretation of facts, and their logical order, may vary greatly, and even alter fundamentally, with the advent of new data or new discoveries. III. In the interpretation of vital phenomena, the physiologist seeks to apply the known laws of physics and chemistry, starting from the obvious position that organised bodies cannot lie beyond the scope of the laws of Nature. The interpretation of these laws is entirely based on the atomistic hypothesis of matter, with its corollary that the indivisible elements of which matter is com- posed are in themselves indestructible and invariable in their fundamental properties, having, i.e., the same specific weight, the same valency or saturation capacity, the same affinity. The energy of which the atoms are the seat may be potential or kinetic. The former is transformed into the latter, and vice versa, INTKODTJCTION 5 either without change of the atomic groups (physical phenomena), or with changes in the same (chemical phenomena). These great empirical laws of the Conservation of Matter (Lavoisier, 1789) and the Conservation of Energy (J. E, Mayer, 1842 ; Helmholtz, 1847) dominate living as well as non-living Nature. A living being objectively considered may be conceived as a machine transforming the matter and energy it derives from the external world. As a physico - chemical science of life, physiology will have fulfilled its task when it is able to provide an adequate mechanical representation of the inner processes which underlie the vital somatic phenomena, that is, when it succeeds in giving a satisfactory explanation of these phenomena, and in describing the processes on which they depend as links in the causal chain of the grand Procession of Nature. The immense value of atomic and molecular mechanics, considered as the basis of vital phenomena (i.e. Physiological Materialism in the modern and scientific sense), is best appreciated in reviewing the vast and rapid progress made by physiology, since it has applied the positive methods of physics and chemistry to the study of life, and has abjured the vain abstract speculations used and abused at the beginning of the last century by the so-called " natural philosophers." At the same time no sincere worker in the positive or scientific .direction can deny that the specifically vital somatic phenomena, i.e. those by which living beings are differentiated from inorganic bodies, are inexplicable by the known laws of chemistry and physics, and that the psychical phenomena (of sensibility and consciousness), which for each individual constitute the culminating point of life, are altogether remote from any mechanical explana- tion : they cannot in any way be regarded as necessary links in the chain of cause and effect in the natural processes of Nature. It is probable that not a few of the still unexplained physio- logical phenomena will become intelligible in the further progress of physics and chemistry ; but even so, such phenomena as are specifically vital, and psychical phenomena, will remain refractory to any mechanical explanation. The dynamic finality proper to living beings (which is essenti- ally distinct from the static finality of the cognate parts of a machine created by human industry) : the capacity for repro- duction, reintegration, adaptation ; the innate tendency to evolve, to progress, to become perfect, with relative independence of environmental conditions, these and other specific phenomena of living beings must, to all who are emancipated from theoretical dogmatism, appear irreducible to a simple play of physical and chemical energies, irreconcilable with the iron necessity of mechanical laws. This is the position assumed by Neo-vitalism, which starts from this affirmation and transcends the earlier 6 PHYSIOLOGY Vitalism, inasmuch as it recognises the experimental method as the exclusive means of scientific progress. When, on the other hand, we consider psychical phenomena (sensibility and consciousness), the impossibility of reducing these to physical and chemical processes becomes even more apparent. Ostwald (1902) has recently attempted to formulate a unitary conception of the world by excluding the materialistic postulates of natural science, i.e. by eliminating the chemical concept of the atoms and substituting the physical concept of energy, psychical processes being regarded as special manifestations of energy. This Energetic Monism of Ostwald is, however, illusory. It is a new and degenerate presentation of the old Idealistic Monism of Hegel, in which the word energy is substituted for the empty word " idea," although equally devoid of definite content. In what, then, does the essential difference between the various forms of physical and that of the supposed psychical energy consist ? In that the former are perceptible solely by the mediation of the senses, the latter by introspection alone the first being objective, the second subjective phenomena ? It is, however, precisely in this antithesis that the vulgar dualistic doctrine of the corporeal as distinct from the spiritual world arises. This theory, which was adumbrated by primitive man from his observations of death (as appears from ethnological and prehistoric studies), became, in the course of centuries, deeply embedded in the mind of the whole civilised world, resisting like a granite block the most potent and repeated attempts of scientific and philosophical critics to dislodge it. Du Bois-Keymond says in this connection: "It is fundamentally impossible to explain by any mechanical means why the note of a Konig's tuning-fork gives me pleasure, while contact with red-hot iron gives me pain " (1872). A more profound (but in our opinion no less illusory) attempt to arrive at a monistic conception is that put for- ward by Mach in his well-known Analysis of the Sensations, and the Relations of the Physical and Psychical (3rd ed., 1902). According to Mach the dualism between body and soul exists in appearance only, and results from a superficial observation of reality. More profound reflection shows that the ultimate elements of reality are nothing but sensations. The entire corporeal world, organic or inorganic, is for us nothing but an aggregate of sensations ; the whole of our thought is similarly constituted of a more or less complex combination of sensations. Hence there is no reason to postulate an essential difference, still less an antagonism, between the physical fact and the psychical fact ; the one like the other, in last resort, results from homo- geneous elements. The disparities are in appearance only, and depend upon the different construction of the aggregates, while the elements of these are quantitatively identical. INTRODUCTION 7 It is obvious that if this mode of philosophising (which recalls the mystical phenomenalism of Berkeley with his " esse est percipi ") is to give us a monistic representation free from all hypothesis, not only the chemical concept of atoms, but also the physical concept of energy must be given up, the psychical concept of sensations alone being retained as the ultimate homogeneous and irreducible element of reality. To be strictly logical, we must cancel the entire doctrine of physics and chemistry, as based upon mere hypothesis, and throw ourselves into the arms of pure psychology, which alone enjoys the privilege of having for its content the aggregates of the homogeneous elements of reality ! But how can we understand the manifold qualitative differences in these aggregates, if once we admit them to arise from qualitatively identical elements ? How conceive of physical facts, and what in common parlance is called the " external world," as a complex of sensations, if we make an abstraction of the internal world, by means of which alone these are to arise as such in consciousness ? How can the physiologist imagine a sensation as divorced from the law of causality and independent of the stimulus that excites it ? Is it not absurd to admit an essential identity between the esse and the nosse, the esse and the posse ? How are we to reconcile Mach's view, according to which the psychical fact is presented as something less real than --almost (as it were) a shadow of the physical fact, with his general doctrine, according to which the physical and the psychical are said to be identical in their nature ? If we inquire from the followers of Mach what pragmatic value can attach to Psychical Monism (or Phenomenalism, or Empirical Criticism, as it is termed by others) they admit that it is nil when we are concerned with scientific work in the various fields of research. " Here all remains as before " (writes Max Verworn, 1905), " methods, symbols, facts, relations are all untouched. Scientific work pursues its course unchecked." This is equivalent to an admission that both the atomistic and the energetic hypotheses (which constitute Materialism), and the hypothesis of vital or psychical force (which constitutes Neo- ritaUsm}, must continue to function as indispensable instruments, as poles or presumptions necessary to future discoveries and to the progress of science in general. In order to build up science we are constrained to descend from the rarefied regions of abstrac- tion, and to live in the world of concrete facts, grappling with the vital processes in their varied and complex phenomenology, whether mechanical or psychical ; in other words, Monism must be completed by Pluralism, according to our immediate experi- ence. Each new physiological experiment, each new scientific conquest, appears as a more or less important integration of the PHYSIOLOGY science of the living ; it always signifies a process that either tends to apply the mechanical explanation to a supposed vital phenomenon, or brings out the essentially vital character of a supposed physico-chemical phenomenon. The evolutionary process of physiological science has always been in the past, and will always be in the future, a continuous and fruitful struggle between the two opposite tendencies of Materialism and Vitalism. It is a mistake to suppose that either the one or the other will ever win the final victory. Both are one-sided ; both reflect one face only of reality. Life, in its more highly evolved forms, results from their interpenetration and fusion. Seen from without, it is body : felt from within, it is soul : this is the great mystery that Art for ever celebrates a mystery Science, with every possible and conceivable progress in physics and chemistry, with all the experimental methods that it may or might employ, will never be in a position to solve. IV. As the physico-chemical science of living beings, Physiology includes the comparative study of the vital phenomena of plants, animals, and man. Some vital phenomena are common to all living beings, without distinction of species, genera, classes, or kingdoms. These are fundamental phenomena, that is, they are the simplest and most elementary in life. Their material substratum is the Cell, i.e. the simplest morphological unit, which Briicke calls the elementary organism, whether living its independent life, or living in association with other cells to form cell aggregates or complex organisms. The physiology of the cell lies at the foundation of all physiology, because the functions of the tissues, organs, and systems can ultimately be reduced to the vital activity of the various cells from which they evolve. Plant physiology, as well as animal and human physiology, derive the fundamental data relating to elementary functions from the physiology of the cell, and employ it as a basis in their study of the complex and special functions of the several tissues, organs, and systems. The science of physiology calls for a different arrange- ment and development, and may assume a different aspect and even content, according as it is approached from a scientific, a philosophical, or a medical and practical standpoint. From the first two it assumes the form and content of general and comparative physiology, which is the necessary complement of general and comparative morphology ; both are directed to the high aim of illustrating, tabulating, and developing the grand doctrine of Evolution or Descent, which from Darwin onwards has been undergoing constant transformation and integration. From the third it assumes the form and content of human physiology, taking Man as the goal of its investigations; it harvests the INTEODUCTION 9 experimental data directly obtained from the higher animals ; it utilises the data derived from pathological observations, which not seldom have a value comparable with that of experiments on animals ; and it dwells with special insistence on such theories as have received or may receive an application to hygiene or preven- tive medicine, and to clinical or curative medicine. Such essentially practical objects are dealt with in this Text- book, which aims at bringing the latest advances in science within reach of all who are working at medicine and at physical and psychological science, and seeks at the same time to equip the younger students, as adequately as may be, with that knowledge of Physiology which lies at the foundation of all scientific culture and education. BIBLIOGRAPHY The following list comprises only such classical Treatises on Physiology as will lie of most use to students in following the historical development of any given physiological question : CLAUDIUS GALENUS. De usu partium corporis Immani. Lib. xvii. A DE HALLER. Elementa physiologiae corporis humani, 1757-66. Auctarium, 1780. Jon. MULLEK. Handbuch d. Physiologic des Menschen. 4th ed. Coblenz, 1844. (French translation with Littre's note. Paris, 1857.) H. MILNE-EDWARDS. Lemons sur la physiologic et 1'anatomie comparee. Paris, 1857-86. F. A. LONGET. Traiti- de physiologic. Leipzig, 1879-81. L. HERMANN. Handbuch d. Physiologic. Leipzig, 1879-81. E. A. SCHAFER. Text-book of Physiology. Edinburgh and London, 1898-1900. W. NAGEL. Handbuch d. Physiologic des Menschen. Brunswick (in course of publication). H. BEATJNIS and V. ADUCCO. Element! di tisiologia umana, comprendenti i priucipii di fisiologia comparata e di tisiologia generale. Turin (in course of publication). CHAPTEE I LIVING MATTER: ITS CHEMICAL AND PHYSICAL BASIS CONTEXTS. 1. The cell-theory. 2. Morphology of the cell. 3. Structure of protoplasm. 4. Structure of nucleus. 5. Chemical elements of the cell. 6. Protein basis of living matter. 7. Classification of proteins. 8. Chemical constitution of proteins. 9. Enzymes or ferments. 10. Classification. 11. Other nitrogenous organic substances, Fats, carbohydrates or saccharides, inorganic substances. 12. Chemical structure of living matter. Bibliography. IN Nature no phenomena can be independent of a material sub- stratum : all are the external manifestation of the energies ini- inauent in matter. Every vital phenomenon that comes under the observation of the physiologist is intimately connected with the living organism, and is the expression of internal causes, i.e. of the different forms of energy inherent within that organism. Whoever, then, approaches the threshold of Physiology in order to study the Manifestations of Life, will feel it essential to have some knowledge of the material substratum out of which the living phenomena have been evolved. I. Both in plants and animals the material substratum of vital phenomena, the physical basis of life, consists of a substance of highly complicated structure and constitution, soft or gelatinous in consistency, to which Hugo Mohl (1846) gave the name of protoplasm. In living beings this does not appear as a simple mass, without form or boundaries ; but it is divided into minute particles, or separate entities, known as cells. Each cell comes from a pre-existing cell, just as every living being comes from the ovum, which is the primitive cell. The so-called Protista, which are the most primitive form of life (and probably constitute the common stock whence plants and animals have developed) are throughout their whole life represented by a single cell, which assumes various forms and dimensions. In the Metdzoa, on the contrary, the primitive cell, or ovum, gives rise to other similar cells, and these to other cells in turn, which are gradually differ- entiated, transformed, and adapted to the several physiological offices which they serve. 11 12 PHYSIOLOGY CHAP. In the Protista each cell is a distinct and independent physio- logical individual ; in the Metazoa each cell or cell-derivative is still a distinct individual, but it is no longer independent, since the life of each is more or less bound up with the life of the others with which it is associated. The individuality of the social aggre- gate, or that of the organism as a whole, is but an individuality of a higher order, i.e. it is the sum of the life of eacli elementary organism. This is essentially the Cell Theory, formulated by Schleideu (1838) and Schwann (1839), reinforced and developed by Virchow (1855), and fully couh'rmed by later observers. Yet among living physiologists there are not wanting some who believe that we must recognise a more radical difference between the independent unicellular organisms and the cells of which complex organisms are built up. The latter, it is said, since they are incapable of living apart from the body of which they form a part, do not constitute a real individual, so that the name of elementary organisms given them by Briicke is inappropriate. Since the several physiological functions essential to life are very unequally divided among the various cells of which the complex organism consists, they must each represent a physiologically simpler unit, and are not therefore comparable with the cells that constitute a true individual, and which are capable of living independent of other cells (E. Schenk and J. Loeb). There is a certain amount of truth in this observation, but the conclusions deduced from it, i.e. the negation of the cell theory, are somewhat far-fetched. In the first place it should be noted that incapacity to live independent of other cells cannot be predi- cated of all the cells of which multicellular organisms are composed ; it rises gradually with the zoological scale (cf. Chap. III. 12). It should further be observed that the life of every organism is invariably conditioned by its special environment, so that it perishes when transported into other media too unlike those in which it normally exists. In unicellular organisms the environment is represented by the sum of the nutritive materials and the stimuli which reach them from the external world : in the cells of which multicellular organisms are built up the medium is represented by the sum of the nutritive matters and the stimuli which reach them, either from the external world or from the other cells with which they live in association. Lastly, in the first as in the second kind of cell a different grade or trend of development may be observed for each of their vital functions. For the rest, the cell theory, which affirms a certain functional autonomy of the morphological elements of which the organism as a, whole consists, is founded on a synthesis of experimental facts that can be easily verified. (a) The survival for a certain time of parts detached from a living organism. LIVING MATTER 13 (&) The non-synchronous death of the several tissues or organs of which the organism is composed. (c) The localisation of the effects of toxins and pathogenic causes. (cT) The possibility of transplanting and grafting tissues and organs. (e) The possibility of multiplying not only plants, but also many of the lower multicellular animals, for instance the fresh- water Hydra by merotomy, or division into segments. II. The organisation of a perfect cell, capable of living and reproducing itself, requires not merely a simple lump of proto- plasm, as was originally maintained by M. Schultze (1863) and subse- quently by E. Haeckel (1870), but the interior of the protoplasmic mass must also contain a nucleus, a con- stituent already described by previous observers as an essential part of elementary organisms. The later work of Gruber (1888) on Ehizopoda and of Biitschli (1890) on Bacteria, has shown that these also consist of two characteristically differentiated parts, corresponding to the cell proto- plasm or cytoplasm, and the nucleus of the perfect cell. The membrane which envelops the protoplasm cannot be regarded as an essential part of the cell, because while rarely absent in plants, it is almost always lacking in the animal cell. The centrosorne FIG. i. A,,webr> proteus. described by van Beneden and Boveri (1887), and considered by them to be the third element of the cell, appears from the more recent work of Hertwig (1891) and Brauer (1893) to be part of the nuclear substance, which is generally extruded into the cytoplasm during the activity of the nucleus, to incite germination and cell division. The morpho- logical concept of the cell is accordingly very simple : it is funda- mentally a lump of protoplasm which includes a more or less distinct nucleus. The importance of the nucleus to the life of the cytoplasm can be demonstrated experimentally, as also the importance of the cytoplasm to the life of the nucleus. The first experiment consists in bisecting a unicellular animal, e.g. an Amoeba (Fig. 1), in such a way that one half contains the nucleus and the other is deprived of it : and then observing under nucleus ; w, contractile vacuole ; i, ingesta ; assing into state of myxamoeba ; ?', (', younn myxamoebae ; /,, /., adult myxamoebae ; /, adherent myxamoebae ready to fuse ; m, young plasmodium ; -n, portion of adult reticulated plasmodium. a membrane or not. Many permanent forms repeat the temporary shapes assumed by the amoeboid cells. The size of the cells, again, varies greatly, though they are almost always of microscopic dimensions. The smallest Bacteria measure only a few thousandths of a millimetre, while the largest Amoebae exceed a tenth of a millimetre. The cells of the higher organisms, Man included, are rarely more than eight hundredths LIVING MATTER of a millimetre in their largest diameter. Muscle fibres, indeed, both plain and striated, may measure more than a decimetre, and the nerve processes of the ganglion cells more than a metre. Still the amount of living matter contained within a cell is always, comparatively speaking, very small. In a bird's egg, which is a single colossal cell, the active, living protoplasm consists only of one very delicate layer, the whole of the rest being inactive yolk, which is destined to feed the germ during its embryonic development. III. Both in animal and in plant cells, protoplasm has the same common properties : it appears as a semi-fluid, almost always colourless substance, with no apparent morphological structure, although it contains a variable quantity of small punctiform gran- ules ; it is readily permeable by water, which swells it up without dissolving- it ; impenetrable as ~rnc * a rule to colouring FIG. 6. Epithelial cell from intestine of insect larva. (Carney.) me, cell membrane ; j>e, cell protoplasm in form of net- work with granulations; mn, nuclear membrane; pn, nuclear protoplasm with a-chromatic, reticulated substance ; bn, skein of chromatic substance in centre of nucleus. matters during life, it stains readily after death. When at rest it has an alka- line reaction, which may become neutral or even acid during activity. The hya- line, non-granulated protoplasm often forms in the cell a more or less dense external layer,known as ectoplasm or hyaloplasm, to distinguish it from the internal granular portion that surrounds the nucleus, the so-called endo- plasm or granuloplasm (Fig. 1). Under the high power of the microscope, this apparently homogeneous protoplasm shows a very complicated structure. Reniak (1844) and M. Schultze (1871) affirmed that there was a fine fibrillar structure in the protoplasm of the ganglion cells of the nervous system, a theory subsequently extended to epithelial, glandular, and other cells. Froniman (1865) and Heitzmann (187->) modified this statement, and assumed a finely reticulated structure, in which the granules would be the nodal points of the protoplasmic network. Carnoy (1883), while admitting the theory of a reticulum, affirmed that the granulation represented not the network but the fluid contained in its meshes, to which he gave the name of enchylema (Fig. 6). Finally, Biitschli (1892) showed VOL. I c 18 PHYSIOLOGY THAI 1 . that the reticulum existed in appearance only, and was merely the optical expression of the finest vesicles in close apposition. Pro- toplasm thus consists of a foam-like ground-substance, constructed . F IG . 7. Alveolar structure of protoplasm. (Butschli.) , Delicate foam of alveolar structure obtained by prolonged whipping of olive oil and cane-sugar ; b, alveolar structure of intra- capstilar protoplasm from Thalassicolla nm-h-ain, as in Fig. 2. in the form of delicate polyhedric vesicles or alveoli, closely pressed together. The protoplasmic granules lie in greater or less num- bers at the corners of the foam-bubl >les, never in the liquid of the alveoli themselves (Fig. 7). Even under the low power, apparently homogeneous protoplasm not infrequently exhibits drops of fluid, or vacuoles, as they are somewhat infelicitously termed. Such accidental vacuoles must be distinguished from the permanent ones, which are so numerous and conspicuous in certain plant cells as to give a spongy appearance to the protoplasm (Fig. 8). Ehythmically pulsating vacuoles may sometimes be observed ; these empty themselves on contracting, and refill with fluid on dilating. This is especially the case in certain kinds of Amoebae, and is very frequent among the ciliated Infusoria. In these cases the vacuoles function as a centre of circulation for the protoplasmic fluid. Besides the vacuoles, there are in vege- table protoplasm granules of chlorophyll, FIO. s. Ceil from staminai starch, and aleuron : in animal protoplasm, hair of Tradescantia f a globules, accumulations of glycogen, and inrgtnica. (Strasburger.) j> & mi. 11 The nucleus is surrounded granules known as vitellm. The chloro- wWe meshes. 1 " phyll corpuscles are of capital importance to the plant cell, since the most characteristic part of its vital processes depends on them ; viz. the reduction of carbonic acid, and fixation of carbon. The granules of starch, aleuron, fat, glycogen, and vitellin are nutritive materials, products of protoplasmic activity, stored up within the cell. i LIVING MATTEE 19 Lastly, it should be noted that the unicellular animals which have no membranes, such as amoebae, leucocytes, infusoria, and other cells, often contain food-stuffs or other solid bodies which they have ingested, e.g. diatoms, small algae, bacteria, etc. (Metschnikoff), which are gradually digested, and appear as solid inclusions in the protoplasm (see Fig. 1). IV. Many of the peculiarities which we have noted in the constitution or structure of the cytoplasm are characteristic of the nucleus also. This is usually a vesicular body, surrounded by a membrane ; at other times it may assume various forms, and may lose the enveloping membrane which divides it from the cytoplasm. Under a high magnification Biitschli detected an alveolar structure similar to that of the cytoplasm, which presents the appearance of a reticulum. The vesicles contain the nuclear fluid ; the substance which forms them is termed a-chromatic, since it does not stain with carmine, haernatoxylin, or other dyes. Another substance, peculiar to the nucleus, which does stain with dyes, and is termed chromatic, can also be distinguished. This appears in the form of small granules or filaments, threads diffused at the nodal points of the a-chromatic substance, or collected in a heap or kind of central skein (see Fig. 6). V. Chemical analysis of animal and vegetable organisms has shown that the elements which enter most constantly and abundantly into the composition of the cell are : Name. Symbol. Atomic Weight. Carbon . . C 12-00 Nitrogen . . N 14-04 Sulphur . . S 32-07 Hydrogen .^ H I'OO Oxygen .... .0 16 -00 Phosphorus . P 31 -00 Chlorine Cl 35-46 Potassium . K 39-14 Sodium . Na 23-04 Magnesium . Mg 24'00 Calcium . Ca 40-00 Iron . . . Fe 56 '00 In addition to these twelve principal elements, other elements occur, but in relatively smaller quantities ; they are not present in every cell, but only in certain special plants and animals. These are : Name. Symbol. Atomic Weight. Silicon ... Si 28-19 Fluorine . . F 18-98 Bromine .... Br 79-76 Iodine I 126-55 Aluminium . . . . Al 27-00 Manganese . ... Mn 53'90 Lithium Li 7'00 20 PHYSIOLOGY CHAP. Name. s\inll. Atomic Weight. Copper . . Cu 63-17 Lead . Pl> 206-47 Zinc . . ZIL 64-90 With the exception of silicon, which is widely distributed in both kingdoms, fluorine, which in small but constant quantities- enters into the chemical composition of the enamel of the teeth, and iodine, which has lately been found in one of the constituents of the thyroid gland, it is probable that all these elements are without physiological significance to the cell-body in which they are found, and that they enter accidentally, like many other extraneous elements, e.g. drugs, toxins, or such as are merely indifferent bodies. It is worth noting that the twelve principal elements that enter constantly into the composition of cells have all a low atomic weight. Nine of them, in fact, belong to the first three series of MendelejefFs Periodic System, and only three (potassium, calcium, iron) belong to the fourth series of the system. Further, these are all found either in the state of elements or as very simple inorganic combinations, which are widely diffused in the air, in water, and in the upper layers of the soil the only habitat of flora and fauna. VI. The chemical compounds of which the cell is built up may be divided into organic and inorganic. Organic substances are distinguished as nitrogenous and non-nitrogenous : the former include the Proteins and their derivatives, the latter the Fats and Carbohydrates. Proteins are the most important organic substances, and are indispensable in the constitution of living protoplasm. They are essentially distinct from carbohydrates and fats in their element- ary composition, for in addition to carbon, hydrogen, and oxygen they contain nitrogen and sulphur. Their molecular structure, and the exact number of atoms of the several elements which enter into their constitution, are still unknown to us. There is, however, no doubt that the molecular structure of these sub- stances is highly complex ; more so, perhaps, than that of any other chemical substance, since the ratio of the number of the various atoms reaches a very considerable figure. It should be noted that the five elements above mentioned are found in the different proteins in much the same proportions, as appears from the following table, which gives the limits between which the percentages of the various elements of protein oscillate : C 50 - 55 mean 52 per cent. H 9-5- 7-3 7 N 15 -17-6 16 O 19 -24 23 S 0-3 - 2-4 2 ] LIVING MATTER 21 These figures, of course, throw no light on the grouping of the respective elements ; i.e. the chemical structure of the protein molecule. They show, however, that the different proteins form a well-defined class of chemical compounds, having a strict relation among themselves, as is further apparent from the physico-chemical properties common to the several members, as follows : (a) Non-diffusibility through the pores of animal or vegetable membranes and of artificial parchment ; they belong, therefore, to the class of bodies which Graham termed colloids. They are obtained in a crystalline form with difficulty, and only by special methods. If the colloid is fluid it is termed sol ; if solid, gel. Liquid and solid gelatin are examples of these two states. When water is the medium in which the colloid is dispersed the terms hydro sol and hydrogel are used respectively. Besides the proteins, many inorganic substances can exist in a colloidal form, e.g. colloidal metals, silicic acid, etc. There has been much recent discussion as to the state in which the colloids exist in a solvent (which in the case of the proteins of the living body is exclusively represented by water). According to the latest conclusions, we are here concerned not with true solutions having the well-known properties of solutions, due to the mixing of the soluble crystalloids, salts, urea, glucose, etc., with water but rather with very fine emulsions or suspensions, i.e. the particles of the colloid substance can be seen in a separate state, suspended in the liquid, and do not enter into those intimate relations with the solvent on which depend the physico-chemical characters of true solutions (osmotic pressures, homogeneity under high magnification, etc.). In fact, these colloidal solutions scarcely lower the freezing-point of the solvent, and under the ultra-microscope are seen to consist of various-sized granules moving in the body of the fluid. (&) All proteins have, further, very definite chemical properties, by which they are sharply differentiated from all other known chemical aggregates, crystalloids or colloids. Their aqueous solutions are optically active, since they deflect the plane of polarised light to the left. Heat, the addition of small quantities of mineral acid, salts of the heavy metals, as also absolute alcohol, solutions of tannin, phosphotungstic acid, picric acid, etc., pre- cipitate and often coagulate them (albumins and globulins). In this case the protein molecule undergoes profound changes, for after removal of the precipitating agent the initial state of col- loid cannot be restored ; the protein is said to be de-natured. Proteins are further precipitated by saturation of the solvent with salts of the alkalies or alkaline earths (sodium chloride, magnesium sulphate, ammonium sulphate). It is important in the chemistry of the proteins to note that in the precipitation determined by these salts the proteins are not de-natured, or at any rate become PHYSIOLOGY CHAP. so very much more slowly for they re-dissolve on removal of the salts by which they were precipitated. All proteins give specific colour reactions. The best known are the following : Milton's Reaction. On adding a solution of mercuric and mercurous nitrate and nitrite in nitric acid (Millon's reagent) and heating, the white precipitate first formed turns red. Xanthoproteic Reaction. On heating with nitric acid the solution of protein turns yellow, and then, on the addition of ammonia, orange. Molisch's Reaction. On adding a few drops of a-naphthol and running in concentrated sulphuric acid, under the solution, a violet ring appears at the junction of the two fluids. If alcohol, ether, or potash be now added it turns yellow. The substitution of thymol for a-naphthol gives a fine rose carmine, which gradu- ally becomes green. Biuret Reaction. A few drops of 2 per cent copper sulphate added to a solution of protein made alkaline with caustic potash or soda, produces a clear violet colour in the cold. Proteoses and peptones, which are the primary decomposition products of the more complex proteins formed by the action of proteolytic fer- ments (infra), give a pure pink colour. Sulphur Reaction. On warming with potash and a little lead acetate, the white precipitate which first appears (lead hydroxide) turns brown and then black, owing to the formation of lead sulphide. These colour tests for proteins are important, not merely as showing the presence of protein, but because they prove the existence in the complex molecule of certain definite chemical compounds to which the several reactions are due. The sulphur test, e.g., indicates the presence of cystine which contains this element ; Millou's test, of the tyrosine group ; the xanthoproteic test, of aromatic groups ; Molisch's reaction, of a carbohydrate : and so on. In fact, these chemical aggregates respectively always give these identical reactions, which are accordingly known as " constitutional tests." The biuret reaction is the most general test for proteins, since it is given by all the proteins and their most immediate derivatives (the proteoses and peptones). It is given, by biuret and other compounds which contain CO.NH groups. It is also given by some of the less complex derivatives (polypeptides), but not by the ultimate products of their decomposi- tion (amino-acids). VII. Owing to our inadequate knowledge of the exact chemical constitution of the different proteins their classification is still based principally upon their physical or physico-chemical properties, e.g. solubility in water or in certain salt solutions, the temperature at which they coagulate, etc. The Chemical and i LIVING MATTEE 23 Physiological Societies of Great Britain adopted the following scheme of classification in 1907 x : I. Protamines, e.g. salmine, sturine. II. Histories, e.g. thynius histone. III. Albumins, e.g. ovalbumin, serum albumin, various vegetable albumins. IV. Globulins, e.g. serum globulin, tibrinogen and fibrin, myosinogen and myosin. Vegetable globulins. V. Glutelins, e.ff. wheat elutelin) VI. Gliadins,V wheat gliadin /l )resent onl y m cereak VII. Phosphoproteins, 2 e.g. caseinogen, vitelliu, iclithulin. VIII. Scleroproteins, 3 e.g. collagen and gelatin, keratin, elastin, fibroin, spoiigin, amyloid, albumoicl, pigments. IX. Conjugated proteins. These are combinations of protein with other compounds. (a) Nucleoproteins. (6) Chromoproteins, e.g. haemoglobin. (c) Glucoproteins. X. Derivatives of proteins. These are formed from members of the other groups by the action of acids and alkalies, or enzymes. , > Ar , facid albumin. (a) Metaprotem- Ulkali albumhli (6) Proteoses : album ose, globulose, caseose, gelatose, etc. (c) Peptones, e.g. fibrin peptone, caseo-peptone, etc. (d) Polypeptides, e.g. glycyl-1-tyrosine, d-alanyl-glycine, 1-leucyl- d-glutamic acid, d-alanyl-1-leueine, etc. The majority are synthetical compounds. Several have now been isolated from proteins. Albumins are coagulable proteins, soluble in distilled water, in dilute salt solutions, in acids and bases, and they are not precipi- tated by saturating the solutions with neutral sodium chloride or magnesium sulphate when the solution is neutral, but they are precipitated by these salts when the solution is acid. They are precipitated by saturating the solution with ammonium sulphate. Globulins are coagulable proteins, insoluble in distilled water and dilute acids, soluble on the other hand in solutions of neutral salts and dilute bases. They are precipitated on saturation with magnesium sulphate and to a certain extent with sodium chloride ; with ammonium sulphate they are precipitated at a lower degree of concentration ( = saturation) than that required to precipitate albumin. The vegetable globulins differ in many respects from the animal globulins ; they have a great tendency to crystallise, and ;have been prepared in large quantities in a crystalline form (Osborne). Fibrinogen and myosin will be discussed in the chapters on Blood Plasma and Muscle. Phosphoproteins are characterised by the fact that phosphorus enters into their composition, so that formerly they were erroneously classed with the nucleoproteins. They are distinct from these 1 Substituted by translator for 0. Cohnheim's (1904) scheme. 2 Formerly nucleoalbumins. 3 Formerly albuminoids. 24 PHYSIOLOGY CHAP. inasmuch as they contain no xanthine or purine bases, which are characteristic of nucleoproteins. They differ from nucleoproteins also in that the phosphorus is completely removed, as inorganic phosphoric acid, by treatment with 1 per cent caustic soda at 37 C. for 24 hours (Plimmer and Scott). The phosphoproteins have the properties of acids ; they turn blue litmus paper red, and are soluble in distilled water only in the form of their alkaline salts, from which solutions they can be precipitated by the addition of stronger acids. Solutions of their salts do not coagulate with heat. Histones, on the contrary, have the character of weak bases, their solutions being precipitated by alkalies. The protamines form a very definite group, differentiated in not a few particulars from the rest of the proteins : they do not contain sulphur, and are richer in nitrogen and poorer in carbon than the other proteins. They are distinctly basic in character, more so than the histones. They have been isolated from the spermatozoa of many fishes (salmine, clupine, scombrine, sturine, etc.). We shall deal with the derivatives of the proteins, more particularly with the proteoses and peptones, which result from the action of the proteolytic ferments on the more complex proteins, in the chapter on Digestion. The conjugated proteins are combinations of a protein with a chemical aggregate, which is not a protein, and which Hoppe- Seyler termed a " prosthetic group." In the nucleoproteins dis- covered by Miescher and Bloss (1871) in cell-nuclei, this prosthetic group is represented by nucleic acid : nucleoprotein therefore results from a combination of protein and nucleic acid. The nucleic acids are organic acids which contain phosphorus and nitrogen, but no sulphur, their chemical constitution being un- known. Their decomposition products, on the contrary, are known to us : these are phosphoric acid, purine bases (adenine, guanine, hypoxauthine, and xanthine), pyrimidine bases (thymine, uracil, cytosine), pentoses (laevulinic acid). Of the various proteins which are able to unite with the nucleic acids to form nucleoprotein, the protamines and histones are the principal. These enter into the molecules of the nucleoproteins of fishes' testicles. Nucleic acid is also combined with histone in the leucocytes of the thymus and the nucleated red corpuscles. Nucleoproteins have distinct acid properties : they are soluble in water and in saline solutions, still more in alkaline fluids ; they are precipitated on the addition of acids, but are redissolved by excess of mineral acid. Haemoglobin (to which we shall return in discussing Blood) results from the combination of a histone (globin) and a complex chemical aggregate containing iron (haematin). i LIVING MATTER 25 Glucoproteins are conjugated proteins, consisting of a carbo- hydrate radicle combined with protein. The nature and consti- tution of this carbohydrate group is unknown. It appears to be a polysaccharide, since it does not reduce : it contains an amiuo group (NH 2 ), for when boiled with acids, it usually yields gluco- samine. The group of proteins known as the scleroproteins includes a series of substances which have few physical properties in common with the preceding groups, but share many other characters with them. They never form part of the animal cell, but compose the skeletal or supporting substance for the cells and organs of the body : they belong to the histological group of the connective tissues in the widest sense of that term. There are no sclero- proteins in the tissue fluids of animals' blood, lymph, etc. The concept scleroprotein is essentially morphological, and from a chemical point of view includes most various bodies. As proteins, the scleroproteins have many properties in common with the other groups. By the action of acids or of proteolytic ferments they are split into proteoses, peptones, and anaino-acids ; they form salts ; and they have the same percentage composition and give the same colour reactions. Of the various scleroproteins enumerated in the table, we may say that collagen is the general substance of bone, cartilage, and connective fibres ; on boiling, it takes up water and is transformed into gelatin. Keratin, the ground substance of the cornea, is an elaboration product of the epidermic cells of the cutis. Elastin, a component of the fibres of elastic tissue and the ligamentum nuchae, is a product of connective tissue cells. Fibroin, the principal component of silk, is an elaboration product of the spinning gland of the silkworm. Spongin is the organic support- ing substance of the bath sponge. Conchiolin is the organic matrix of the snail and other molluscs. Amyloid, lastly, is a substance which is absent in the healthy organism, but accumulates in enormous quantities under the influence of various pathological degenerative processes. Albumoid is the name which has been given to many different substances found in various organisms, e.g. the membraua propria of certain glands, the vitreous membrane, sarcolernnia, the solid constituents of the lens, scales of fishes, etc. These are also scleroproteins. Lastly, the group of pigments, or melanins, includes all those various pigments, brown, black, chestnut, etc., which determine the characteristic hue of hair, fur, and choroid, and which are found in the so-called melanotic tumours. VIII. The analytical and experimental work on the chemical structure and constitution of proteins, as recently carried out by such distinguished physiological chemists as Kossel, Hofmeister, 26 PHYSIOLOGY CHAI-. and more particularly Fischer and his school, has led within the last few years to important results. While these do not as yet account fully for all the different chemical units which build up the complex protein molecule, they represent a great advance in this direction. A brief review of this work, which has profoundly modified most of the theories previously held by physiologists, is essential. The analytical method is invariably employed in investigating the chemical structure of highly complex bodies. The complex substance must be decomposed and split up into its simpler constituents, i.e. into the units of which it is built up. For proteins, hydrolytic cleavage is the method of artificial decom- position that gives the best results, i.e. decomposition with absorption of molecules of water. This hydrolytic cleavage or hydrolysis of proteins may take place by the prolonged action (a) Of mineral acids, by boiling the protein with concentrated hydrochloric acid or 25 per cent sulphuric acid for twelve to fifteen hours (method proposed by Fischer, and generally used in his laboratory) ; (6) Of alkalies ; and (c) Of proteolytic ferments. The most important result of all the researches into hydrolytic cleavage up to the present time is that even the most unlike proteins have, among themselves, a very similar constitution, judging from the end products. These are invariably the same, no matter what process of hydrolytic decomposition is employed. It was formerly believed that one essential difference only existed between hydrolysis by the proteolytic ferments and that by acids and alkalies : the disintegrating action of the ferments was supposed to be more gradual, since before reaching the final products of cleavage, which no longer yield the biuret reaction, those intermediate cleavage products were obtained which are known by the name of proteoses and peptones (of which we shall treat fully in the physiology of Digestion). These products were supposed not to appear in the cleavage effected by strong acids and bases, but complex products with similar properties have now been isolated and studied by Fischer and Abderhalden. Some of the final products of cleavage are still unknown ; most of them, however, have been isolated and identified. They are the organic compounds known as amino-acids, or organic acids, in the molecule of which an amino-group (NH.,) is substituted for one or more atoms of hydrogen ; our knowledge of the various ammo-acids that arise from proteins by cleavage is mainly due to Fischer, who has devised new methods for their isolation and recognition. The number and variety of the arnino-acids at present isolated is shown in the following table of Abderhalden : LIVING MATTEE I. AlipJi'iffc i>r Fulfil N,T/V.,-. 1. Mono-amino-mono-carboxylie acids : glycine alanine valine Itmeine isoleucine. 2. Mono-amino-oxy-mono-cai'boxylic acids : seriuc. 3. Mono-amino-thio-mono-carboxylic acids : cysteine and cystine. 4. Mono-amino-di-carboxylic acids : aspartic acid glutamie acid. ">. Di-amino-mono-carboxylic acids : lysine arginine. 6. Di-ainino-uxy-mono-cai'boxylic acids : di-amino-tri-oxy-dodecanic acid. II. Aromatic Series. 1. Mono-amino-mono-carboxylic acids : plieiiylalanine. 2. Mono-amino-oxy-mono-carboxylic acids : tyrosinc. III. Heterocyclic Compounds. 1. Mono-amino-moiio-carboxylic acids : proline (a-pyrrolidine-carboxylic acid) tryptopliane (indole - a - ammo - pro- pionic acid) liistidine (imidazole - a - amino - pro- pionic acid). 2 Mono-amino-oxy-monu-carboxylic acids : oxy-proline (oxy-pyrrolidine- carboxylic acid). Some chemists further regard the carbohydrate (glucosamine) group as a cleavage product of proteins : this group, however, occupies a special position, inasmuch as it is absent in many proteins, while in others its presence is doubtful, and, moreover, those which contain large amounts of it are by many considered to be compound proteins (gluco-proteins). We may suppose that as all proteins contain units which exhibit great affinity to the molecule of a carbohydrate, since they contain six carbon atoms, there is a possible transition from this group to the carbohydrate molecule. Lysine, e.g., which is an amino-acid invariably present among the cleavage products of all proteins, has a formula very like that of glucosamine and glucose, as will be seen from the following table : CH 2 (OH) CH(OH) CH(OH) i CH,(OH) CH(OH) CH(OH) CH 2 (NH,) CH 2 CH 2 CH(OH) i CH(OH) i CH, CH(OH) CH(NH 2 ) CH(NH 2 ) CH: CH: COOH Glucose Glucosamine Lysine PHYSIOLOGY CHAP. Returning to the various ammo- acids which represent the products of the hydroly tic cleavage of proteins, we must note the important fact that, with the exception of the protamines, all proteins hitherto decomposed contain the] same units. One or other of the aniino-acids, e.y. glycine in egg albumin and serum albumin, may be wanting, but these are rare exceptions. What differentiates the several proteins among themselves is, -on the other hand, the varying quantitative relations of the differ- ent auiino-acids which compose the protein molecule. In some proteins, certain special amino-acids, e.g, leuciue and more particu- larly glutamic acid, occur in enormous quantities, as in the proteins of plant seeds. There are great differences, again, in the relative proportions of the mono- and di-aniino acids ; the latter are found in large quantities in the protamines, while they are almost absent in some of the scleroproteins. The histones occupy an intermediate position between the pro- tamines and the coagulable proteins (albumins and globulins). From these facts it may be anticipated that we shall before long be able to classify the various groups of proteins on the basis of similar end products. Indeed, from the fact that the same units enter into their constitution, although in different proportions for the different substances, we can even now 7 to a certain extent perceive how the several alimentary proteins may be converted into the other definite proteins of the animal body. It has been objected that the ultimate cleavage products of the artificial hydrolysis of proteins are not really pre-forrned as so many units in the protein molecule : but the various data recently acquired meet this objection. The following may be briefly noted : (a) In whatever way the hydrolytic cleavage of any protein is effected, whether by acids, by alkalies, or by proteolytic ferments, the final products are approximately the same in quality and quantity. Tryptophane is the sole exception, since it is largely destroyed on hydrolysis by acids. (&) Fischer has succeeded in artificially combining two or more molecules of aniino-acid, and has thus obtained synthetically the chemical compounds which he terms polypeptides, which in a number of properties have affinity with the natural proteins. The type on which this synthesis has been successfully carried out is represented by the simplest dipeptide, which is known as glycyl- glycine, and which results from the coupling together of two molecules of glycine (or glycocoll) according to the following equation : NH 2 .CH,.COOH + HNH.CH 2 .COOH = glyciue glycine NH 2 .CH 2 .CO.NH.CH 2 .COOH + H 2 0. glycyl-glycine i LIVING MATTEE 29 Here the basic group (NH 2 ) of one molecule of glycine is united with the acid group (COOH) of the second, with loss of a molecule of water a true polymerisation. It is clear that by the same process another molecule of glycine may be united with this compound (dipeptide), thus making a tripeptide, and so on. If we remember that all other amino-acids are capable like glycine of similar combination between themselves and with the molecules of other ammo-acids, it is evidently possible to obtain a very numerous series of different and more or less highly complex compounds. Fischer and his school have already succeeded in producing synthetically some seventy similar compounds ; the most complex is an octadecapepti.de, which consists of eighteen molecules of ammo-acid united together in this manner. It is important to note that many of these polypeptides, particularly the more complex, give the biuret reaction, which, as we have said, is the most characteristic test of protein, and that some of them are digested by pancreatic juice, which disintegrates them into the amino-acid components, as is the case with natural proteins. IX. Enzymes and ferments must further be included in the protein group, and belong in all probability to the nucleoproteins, or, according to others, the scleroproteins. These, being elabora- tion products of the living cell, represent, according to the latest view (Hofmeister, 1901), the chemical instruments by means of which all chemical changes of the different substances which form the material substratum of living matter take place. These chemical changes result in the disintegration of the complex molecule into simpler compounds (cleavage by analytical ferments), either by rendering it suitable in form and quality for assimilation, as in the case of the various digestive ferments of the alimentary canal in animals, or by setting free the potential energy which is manifested in the form of heat or movement. To this large class of analytic ferments another class of ferments is opposed, whose work consists not in the chemical cleavage of substances with large molecules, but in synthetic processes, in which simple molecules unite to form more complex molecules, as occurs in the so-called anabolic phase of metabolism in living organisms. The theoretical existence of these supposed synthetic ferments has so far not received any decisive proof. We will therefore content ourselves with a rapid survey of the class of analytic ferments, of which much has been learnt by recent work. The fermentative processes of decomposition were, until recently, divided into two great classes which were very distinct from one another. In the one class were placed all the non-organised ferments or enzymes, which were regarded as the elaboration pro- ducts of the various secreting glands, capable of being isolated, 30 PHYSIOLOGY CHAP. and of acting as pure chemical agents, independent of the living elements which produced them. The several digestive enzymes of the gastro - intestinal tract in animals were considered as examples of these non-organised ferments. The second class comprised the so-called organised ferments, or /erments proper, represented by micro-organisms (fungi, bacteria, etc.), the action of which was then held to be in direct dependence upon the vitality of the latter, and to cease on their death or disorganisation. Saccharomyces cerevisiae, which determines the alcoholic fermentation of glucose (Pasteur), was regarded as the prototype of such organised ferments. Now, however, in consequence of Buchner's work (1899), this distinction can no longer be maintained. Buchner has demon- strated experimentally that it is possible to extract from the cells of beer-yeast, when exposed to enormous pressure, a substance rich in protein, which is free from living elements, and is able to set up the alcoholic fermentation of solutions of glucose. The property by which yeast cells ferment glucose is therefore due, not to a true vital process, but to the action of an enzyme or zymase, produced by the cell. Specific enzymes of other micro- organisms formerly held to be organised ferments (the bacilli of lactic fermentation, of acetic fermentation, etc.) have also been isolated. All enzymes are now regarded as organic substances (most probably of the nature of proteins) which are elaboration products of the living cells, from which they can be separated and extracted by various methods without losing their activity. Generally speaking they can be extracted from the cells and the tissues, on treating these with water or glycerin. The latter solvent, in particular, yields solutions that remain active for a considerable time, and has been largely employed in practice to extract these enzymes. It should be stated that the enzymes are frequently not found pre-formed within the cells which produce them, but are as it were in a potential state. The complete development of their specific enzyme activity necessitates the further action of oxygen and other chemical compounds known as kinases. The mother- substances from which the enzymes are derived are called zymogens or pro-enzymes. We shall discuss these at length in speaking of the digestive ferments, since there is in the intestine a substance which activates the pancreatic enzymes (enter o-kinase). No characteristic chemical reactions are common to all enzymes ; generally speaking, they are precipitated from their colloidal solutions by alcohol, and are destroyed by high temperatures from + 80 to + 100 C. In order to recognise them, it is necessary to observe the properties which characterise their mode of action. In the first place enzymes, in consequence of their i LIVING MATTER 31 peculiar chemical action, do uot form stable combinations with the substances on which they act, or with the decomposition products arising from their activity. An infinitesimal quantity of enzyme is able to act upon a relatively enormous quantity of fermentable substance. It has been found, e.g., that one part of invertase is capable of splitting up 100,000 parts of saccharose, and one part of chymosin or rennet of coagulating 400,000 parts of caseinogen. A second property of enzymes is the specific character of their action, inasmuch as any one enzyme acts only upon a definite substance, or upon a restricted group of allied substances. Enzyme action is always in strict relation with the configuration and con- stitution of the atomic grouping of the relative molecules, to which the enzyme is as rigorously adapted as the key to the wards of a lock to repeat once more the picturesque expression of E. Fischer. This specific action is, in fact, so conspicuous as to serve as a method of distinguishing isomeric chemical compounds from one another. Enzyme action is further influenced by various external conditions, e.g. the reaction of the liquid : some ferments are active only in an acid medium, others and far the greater number in a neutral or faintly alkaline medium. Temperature has a marked influence on the course of enzyme activity, which usually increases with the rise of temperature to a certain point representing the optimum, after which a further rise of temperature diminishes the enzyme action until it disappears. The accumulation of cleavage products has a marked inhibitory influence on the development of enzyme activity ; the inhibition ceases so soon as these products are removed. How is it possible to explain the action of enzymes ? Certain inorganic substances exhibit properties highly similar to those of the analytical enzymes we have been considering, since they are capable of producing cleavage processes which do not essentially differ from processes of fermentation. These sub- stances, which have been known for some time to chemists, are the so-called catalysers, and determine the process of catalysis (Ostwald). A classical example of catalytic action is that repre- sented by the decomposition of hydrogen peroxide (H.,0.,) into oxygen (0) and water (H 0) by platinum black. A trace of this substance will decompose an enormous amount of hydrogen peroxide without any loss of activity. Bredig (1899) has recently enlarged the class of catalysers by showing that all metals in a colloidal state, to which he gives the name of inorganic ferments, belong to it. Moreover, he has brought out so many interesting coincidences between the action of these catalysers and that of enzymes as to render the hypothesis PHYSIOLOGY CHAP. highly probable that both classes of substances act in virtue of the same principle. To Ostwald is due the special distinction of having effectively contributed to our knowledge of the mode of action of catalysers. According to him, every catalytic process consists essentially of a change of velocity in a chemical process, which occurs spontaneously. " A catalyser is a body which, without appearing in the end product of a chemical reaction, alters its velocity by accelerating or by retarding it." This theory is especially applicable to the example cited of hydrogen peroxide and platinum black : we know, in fact, that the hydrogen peroxide slowly decomposes by itself into water and oxygen, to such an extent that after a few days there is no longer any trace of the hydrogen peroxide in an open vessel containing it. The platinum black merely accelerates the spontaneous process of scission. The same thing must occur in the case of enzymes and the substances which they split up. This is not the place for discussion of the various theories put forward to explain the action of catalysers and of fer- ments : it need only be said that nowadays everything points to the conclusion that this action is effected not directly, but by the formation of intermediate products (which do not, however, appear in the end products of cleavage), and that according to Euler enzymes and catalysers act as collectors of ions. X. In the present state of physiology the only possible basis for a classification of the different enzymes is the changes which they effect. According to Hammarsten, the enzymes which have more especially been made the subject of experimental research may be subdivided into two great classes, i.e. hi/drolytic and oxidative. The class of hydrolytic ferments, i.e. those which split up complex chemical aggregates into simpler molecules by the absorption of molecules of water, comprises all the several digestive ferments, which, as we shall see, fulfil the office of disintegrating complex proteins, polysaccharides and alimentary fats into simpler compounds. The latter are better adapted for absorption by the intestinal epithelium, where they are either finally split up, or elaborated into new and more complex chemical compounds by the metabolic activity of the tissues. They are : (a) Proteolytic or proteoclastic enzymes, which split up proteins, and of which we have already spoken. In the animal body there are two (according to some authors, three) different types of proteolytic ferments pepsin, trypsin, and to these, according to some modern workers (O. Cohnheirn), erepsin must be added. We shall deal fully with these enzymes in the chapter on Digestion. Vegetable proteolytic ferments (e.g. papaiu) are also known. LIVING MATTEE 33 Amy .oli/tic enzymes or amylases, which split the poly- saccharides (starch, etc.) into di- or mono-saccharides. To these belong the various diastases of the animal and plant kingdom O J. O (ptyalin, arnylopsin). The so-called invertases which split di- saccharides into mono-saccharides are in close relation with these ;. e.g. maltase which splits maltose into two molecules of glucose ; invertase, which splits saccharose into one molecule of fructose and one of glucose ; lactase, which splits lactose into one molecule of glucose and one of galactose. (c) Lipolytic enzymes or Upases, which split neutral fats into their components, i.e. glycerin and fatty acids. To these belongs the so-called steapsin of the pancreatic juice to which, according to the latest investigations, must be added another lipase, formed by the gastric mucosa. The class of hydrolytic ferments further includes a number of other ferments recently discovered in the tissues and organs of animals and plants, such as arginase, which splits arginiue into urea and ornithine ; adenase and guanase, which split up adenine- and guanine respectively into ammonia and hypoxauthine or xanthine ; mease, which splits urea into ammonia, w r ater, carbonic acid, etc. A special position (which has been little noticed) is occupied by the so-called coagulating enzymes, such as the rennin or chymosin of the digestive tube, which forms casein from the caseinogeu of milk, and thrombin or thrornbase, which determines the clotting of blood by transforming fibrinogen into fibrin, as we shall see in treating of blood plasma. The class of oxidising ferments contains all those ferments which determine the disintegration of complex substances by oxidising them, by a process highly similar to that which occurs in inorganic nature in the various forms of combustion, e.g. of carbon, which burns, combining with the oxygen of the air. These ferments, too, are analytic, i.e. they break down the complex chemical compounds into simpler compounds, making them richer in oxygen derived from the atmosphere or other sources and thereby liberating a certain quantity of potential chemical energy. Great importance is ascribed to these oxidising ferments, as they are the agents of the various processes of oxida- tion, which occur, as we shall frequently find, within the living organism : and it has been possible, by modern methods of research, to isolate a large number of enzymes belonging to this class from animal and vegetable tissues. Direct oxidases (the name given to the oxidising ferments) must be distinguished from the indirect, which are known as- peroxidases. The former are capable of causing oxygen to act directly ; the latter can only oxidise in the presence of peroxides (hydrogen peroxide). Oxidases give a blue reaction VOL. i D 34 PHYSIOLOGY CHAP. directly with tincture of guaiacum, peroxidases only in presence of a peroxide. Some consider as a third group of the oxidising ferments the so-called catalases, which split up hydrogen peroxide into oxygen and water, hut never give a blue reaction with tincture of guaiacum. The alcoholic fermentation of glucose by means of beer yeast, or the ferment known as ztjmase, which was first isolated by Buclmer from the cells of that micro-organism, is not a true and proper oxidation in which free oxygen is absorbed by the sugar- as may be deduced from the fact that such fermentation takes place anaerobically, and according to the equation : < ' (i H,,0 6 = 2C,H 5 OH + 200., Glucose Alcohol Carbonic acid It should rather be considered as an internal or intra-inolecular oxidation, by which part of the molecule of glucose is oxidised, and burns at the expense of the other part, till it finally splits up into alcohol and carbonic acid. According to recent investigation, we have here the co-operation of two separate and distinct enzymes, one of which, lactolase, or lactacidase, converts sugar into lactic acid, while the other, zymase, or alcoholase, splits the lactic acid into alcohol and carbonic acid. According to some authors (whose conclusions have, however, been warmly disputed), a similar anaerobic fermentative process of glycolysis takes place in animal tissues. In conclusion we must mention another class of ferments, of which we know at present even less than those already discussed the so-called reducing ferments, reductases or hydrogenases. Another classification of enzymes is based upon the difference of place in which they normally occur. Thus, to the ferments known as extracellular or secretory, because normally found in the liquids secreted by the various glands or cells, are opposed the intracellular ferments or eudo-enzymes, which are found within the cell, and represent the chemical agents by which the cells are able to split up or fabricate the several chemical components of their substance. To this class of eudo-enzymes belong Buchner's zymase, many of the oxidases, and also a series of hydrolytic, proteoclastic enzymes, which according to Vernon are of the type of 0. Cohnheim's erepsin. To these intracellular proteolytic ferments are due the phenomena of post-mortem autodigestion or autolysis, described for the first time by Salkowski (1900), which occurs in the organs or organic fluids, when isolated from the body, and kept free of bacterial or extraneous enzymatic contamination. After a certain lapse of time it can be shown that protein cleavage has taken i LIVING MATTEE 35 place iii the tissues or fluids, accompanied by a similar cleavage of fats and carbohydrates. The phenomena of post-mortem autolysis have been the subject of numerous recent researches, in the hope of throwing some light upon intra vitam, intracellular, fermentative processes, which we must assume to be of great importance in the metabolism of the tissues and of the living cells. The results so far obtained are not, however, decisive enough to serve as the basis of any definite conclusion. XI. The proteins of living matter are always accompanied by a large amount of simpler substances, nitrogenous or non- nitrogenous, which represent products of decomposition or of retrogressive changes in these substances, or in nutrient substances from outside, which have been more or less elaborated by the activity of the cell. The name deutoplasm has been given to these substances as a whole, that of cytoplasm being reserved for the living substance generically known as protoplasm. The nitrogenous products of the retrogressive metamorphoses of protein form a series of well-defined chemical substances, many of which are eliminated with the urine in very varying amounts in the higher animals. The largest in quantity and in nitrogen content is urea, next come uric acid, hippuric acid, creatine and creatinine. The purine bases form a distinct group already referred to, xanthiue, hypoxanthiue or sarkine, adenine, guanine, and they are the decomposition products of nuclein. These substances cannot all be extracted from the tissues, owing to the minimal quantity in which they are present. Another group of nitrogenous and phosphorised substances, the lecithins, occur, according to Hoppe-Seyler, in every plant and animal cell, and in particularly large quantities in the elements of nerve, the blood corpuscles and in yolk of egg. In its chemical characters (solubility in ether and alcohol, insolubility in water) lecithin shows great similarity to fats. It resembles nuclein inasmuch as it contains phosphorus, and is capable of forming unstable combinations with albumin and other substances. The yolk of egg contains a combination of lecithin with vitellin. Protagon, extracted by Liebreich (1865) from the brain, is the combination of a lecithin with cerebrin, a nitrogen- ous substance free from phosphorus, similar to the glucosides. The non-nitrogenous organic products which enter into the chemical constitution of the cell are represented by the fats and carbohydrates. These originate partly in the consumption of proteins, partly from external food-stuffs, or their transformations as effected by the cell-enzymes. Chemically considered, the fats represent combinations of glycerin (triatomic alcohol) with the acids of the fatty series (stearic, palmitic, butyric, valerianic, caproic), as also with oleic acid, which does not belong to the normal fatty series. 36 PHYSIOLOGY CHAP. Cholesterin resembles the fats in certain of its characteristics, though absolutely unlike them in its chemical constitution ; it is regularly found in every animal and plant cell, particularly in the brain and liver. Since it is a secretion from the skin of man and other animals, it is found in the epidermal structures (hair, fur, feathers, nails, etc.), for which it forms a kind of protective grease. Cholesterin is a inonatoinic alcohol of unknown constitution, which crystallises from alcoholic solution in laminae like mother-of-pearl. Like glycerin, it forms with fatty acids compounds which corre- spond to the fats. From a chemical point of view the carbohydrates are aldehydic or ketonic derivatives of polyhydric alcohols. They may be divided into three groups: (a) monosaccharides, (&) di-saccharides, (c) poly- saccharides. (a) Among the monosaccliarides are more particularly grape sugar (glucose or dextrose) and fruit sugar (fructose or laevulose), which are abundant in plant juices; the first also occurs in animal tissues. They turn the plane of polarised light to the right or left. They are readily oxidised ; they are fermented by yeast, and converted into alcohol and carbonic acid : C (i H 12 6 = 2C,H 5 OH + 2CO., They have the property of readily abstracting oxygen from the surrounding medium, and behave as reducing agents to oxidised compounds. This property is utilised in detecting the presence of sugars, and also in estimating them. The tests most used are Trommer's and Bottger's. In the former the sugar solution, rendered alkaline with caustic potash or soda, on adding a few drops of dilute copper sulphate, and heating, reduces the copper oxide to cuprous oxide, a suboxide which forms a reddish-yellow pre- cipitate. In the second test a few drops of bismuth subnitrate are added to the alkaline solution of sugar, which is turned black by the reduction of the bismuth salt to the metallic state. Besides these two tests, which, since they are based on the reducing property of glucose, are not, strictly speaking, specific to this compound, but are common to all the reducing substances, three other specific tests are known for glucose, namely Moore's test, the phenyl-hydrazine test, and that of alcoholic fermentation (biological test). In the first the solution of glucose is warmed, after diluting it with about a quarter of its volume of caustic soda or potash. The mixture first turns yellow, and then successively (according to the content of sugar) orange, brown, dark brown, giving off the char- acteristic odour of burnt sugar or caramel, which becomes more intense on acidification. The second test consists in warming the glucose solution with i LIVING MATTER 37 acetate of phenyl-hydrazine ; characteristic yellow crystals (needles ) of phenyl-glucosazone are formed (E. Fischer). The biological test is based on the fact that beer yeast is able to provoke alcoholic fermentation in a solution of glucose. We shall give the quantitative tests for glucose in dealing with urine. (&) Di-saccharides have the formula C 10 H., O n , which represents the combination of two molecules of a nionosaccharide with elimination of a molecule of water. The most important are cane sugar (saccharose) and milk sugar (lactose). On warming with dilute mineral acids, and under the action of certain bacteria, the di-saccharides are inverted, i.e. transformed into monosaccharides. Under the fermentative action of the Bacterium lacticum these last are transformed into lactic acid (C 6 H 12 G = 2C 3 H C 3 ). With Bacillus butyricus lactic acid undergoes further decomposition, giving rise to butyric acid, carbonic acid, and hydrogen : 2C 3 H O 3 = C 4 H 8 2 + 2CO, + 4H. (c) Poly sacchar ides are also anhydrides of monosaccharides, and result from the combination of several molecules ; they there- fore have a high molecular weight, which differs in different compounds of the group. Their general formula is wC G H 10 5 . They do not taste sweet, are generally amorphous, are partly soluble, partly insoluble in water, and are convertible into monosaccharides by various means. They include a series of bodies widely distributed in both plant and animal cells. The most important are starch, which in the form of stratified corpuscles is found in the protoplasm of many plant cells ; glycogen or animal starch, which occurs in almost all animal tissues, but particularly in the amorphous granules of the hepatic cells, as also in muscle fibre, embryonic tissue, and proliferating cells in general : animal and vegetable gums; cellulose, which is the principal component of the cellular membranes of plants, and is also found in the animal kingdom in the mantle of Tunicata and the chitinous skeleton of insects. Polysaccharides behave variously to solutions of iodine. The starches turn blue, glycogen brown ; cellulose does not stain at all with iodine, and only assumes a bluish tint on treatment with sulphuric acid. In addition to free carbohydrates, living protoplasm contains other compounds such as rnucin and chitin, as is shown in their derivatives and decomposition products (dextrin, sugar, lactic acid, butyric acid, etc.). The inorganic substance of elementary organisms consists of w r ater, salts, and gases. Water is indispensable to the activity of living matter, since PHYSIOLOGY CHAP. it dissolves the single particles, and renders them capable of being transported. It is present partly in chemical combination, partly as solvent for the various substances of the cell-contents. The amount by weight of water in the tissues is on an average over 50 per cent. According to von Bezold, the total content of water in the human body is about 59 per cent. Bone contains 22 per cent water, liver 69 per cent, muscle 75 per cent, the kidneys 82 per cent. The water holds in solution a number of salts, which are never wanting in living substance. Chlorides largely predominate ; next come the carbonates, sulphates, phosphates of the alkalies and alkaline earths. Such are the chlorides of sodium, potassium, and ammonium ; the carbonates, sulphates, and phosphates of sodium, potassium, calcium, magnesium, and ammonium. A considerable part of these salts is probably in chemical combination with the organic substances. The gases, oxygen, carbonic acid, and nitrogen, when not chemically combined, are simply dissolved in the water ; very occasionally they occur in the form of gaseous vesicles, as in certain unicellular Khizopods. XII. After this bird's-eye review of the vast province of the chemistry of elementary organisms, undertaken solely with the object of classifying into groups and subgroups the several bodies that compose the substratum of the phenomena of life, it must again be emphasised that we are far from any adequate knowledge of the chemical structure of living matter. It is impossible to investigate this living matter without first killing it, i.e. destroying its vitality. The chemical compounds, organic and inorganic, which we have seen to exist in plants and animals, are only the products of this destruction, i.e. they represent the chemical aggregates, which can be recognised and isolated from the dead body. They certainly exist in the cell ; but we are entirely ignorant of the mode in which they are associated and combined among themselves, so as to compose the living matter. JS T or should this surprise us, when we reflect that with the ordinary methods of chemical analysis we have no means of ascertaining the exact chemical nature of the individual salts contained, e.g. in a mineral water. We can only determine the quality and quantity of the acids and bases contained in it ; as to what these salts are, and how they are mixed together, we know nothing. Any state- ments in regard to this are mere guesswork. The physiologist needs to be very circumspect and cautious in applying the data thus derived from the chemistry of dead matter to the phenomena of living substance, in which the chemical relations of the several molecular aggregates are very different, and the molecules themselves are highly complex and excessively unstable. i LIVING MATTEE 39 Immense progress has been made of late years in the know- ledge of the finer morphological structure of the cell, which must help in determining the chemical differences between the protoplasm and the nucleus, respectively. The first advances in this direction are due to the methods of Micro-Chemistry. Kossel's work (1891) has shown that in the nucleus, compounds of protein with substances containing phosphorus largely pre- dominate, while the cytoplasm consists principally of simple proteins and their compounds with combinations which contain no phosphorus. Miescher had previously demonstrated (1874) that the nucleins which he discovered resist the digestive action of gastric juice, and that on placing cells of various kinds in this juice the cytoplasm of the cell dissolves, while the nuclei remain, although of smaller size. Malfatti (1892) next showed that it is the chromatic substance and the nucleolus of the nuclei which do not digest, while the nuclear fluid and a-chromatic substance dissolve. This proves the chromatic substance and the nucleolus of the nuclei to consist essentially of nucleins or their combinations, while the cell protoplasm consists of other proteins. Lastly, Lilienfeld and Monti (1892) showed that ammonium molybdate is a micro- chemical reagent for phosphorus -containing substances, in the presence of which phospho-molybdic acid is formed, which stains brown on the addition of pyrogallol. By means of this reagent it has been ascertained that the compounds of phosphorus, in the most dissimilar cells, are almost exclusively contained in the nucleus. 1 Carbohydrates and fats, on the other hand, are almost ex- clusively localised in the cytoplasm and limiting cell membrane. Nothing is known in regard to the localisation of the inorganic compounds; except that, according to Vahlen, potassium compounds are absent from the nuclei of cells. BIBLIOGRAPHY F. HOPPE-SEYLER. Physiologische Cheniie, I. Teil, Allg. Biol. Berlin, 1877. 0. HERTWIG. Die Zelle u. die Gewebe. Jena, 1893-1898. (English translation, The Cell, Campbell, 1895.) M. VERWORN. Allgemeine Physiologic. 4th ed. Jena, 1906. (English transla- tion, General Physiology, by F. S. Lee. Macmillan, 1899.) R. NEUMEISTER. Lehrbuch d. physiologischen Cheniie. Jena, 2nd ed., 1892. F. BOTTAZZI. Trattato di chimiea fisiologica. Milan, 1898. 0. HAMMARSTEN. Lehrbuch d. physiologischen Cheniie. Wiesbaden, 6th ed., 1907. E. ABDEUHALDEN. Lehrbuch d. physiologischen Chemie. Berlin and Vienna, 1906. E. FISCHER. Untersuchungen iiber Amino-sauren, Polypeptide, n. Proteiue. Berlin, 1896. 1 Scott has shown that it is only the inorganic phosphates which react with this reagent. Organic phosphorus compounds do not react, especially those of the nuclein type, which are not readily hydrolysed into phosphoric acid. PLIMMEII and SCOTT. 40 PHYSIOLOGY CHAP. C. OrPKNiiKiMKR. Die Ferineute u. ihre Wirkungen. Leipzig, Vogel, 1903. <,'. BKEIUG. Die Elemente d. chemischen Kinetik, mit besonderer Beriiok- sichtigung des Ka'talyse n. der Ferment- Wirkung. Ergebnisse d. Physiol., I. Part I., 1901. Recent Englisli literature of the subject : F. G. HOPKINS and S. W. COLE. A Contribution to the Chemistry of Proteids, Part I. Journ. of Physiol., 1901-2, xxvii. 418. P. A. LEVENE and L. B. MENDEL. Some Decomposition Products of the Crystallized Vegetable Proteid cdcstin. Amer. Journ. of Physiol., 1902, vi. 48. A. X. RICHARDS and W. J. GIES. Chemical Studies of Elastin, Mucoid, and other Proteids in Elastic Tissue, with some Notes on Ligament Extractives. Amer. Journ. of Physiol., 1902, vii. 93. W. W. LESEM and W. J. GIES. Notes on the Protagon of the Brain. Amer. Journ. of Physiol., 1903, viii. 183. F. G. HOPKINS and S. W. COLE. A Contribution to the Chemistry of Proteids. Part II. Journ. of Physiol., 1903, xxix. 451. W. CRAMER. On Protagon, Cholin, and Neuriu. Journ. of Physiol., 1904, xxxi. 30. C. SEIFEUT and W. J. GIES. On the Distribution of Osseo-mucoid. Amer. Journ. of Physiol., 1904, x. 146. H. NEILSON. The Hydrolysis and Synthesis of Fats by Platinum Black. Amer. Journ. of Physiol., 1904, x. 191. H. G. WELLS. On the Relation of Autolysis to Proteid Metabolism. Amer. Journ. of Physiol., 1904, xi. 351. E. R. POSNEU. Do the Mucoids combine with other Proteids ? Amer. Journ. of Physiol., 1904, xi. 404. P. A. LEVENE. The Autolysis of Animal Organs. Amer. Journ. of Physiol., 1904, xi. 437 and xii. 276. T. B. OSBORNE and I. F. HARRIS. The Precipitation Limits with Ammonium Sulphate of some Vegetable Proteins. Amer. Journ. of Physiol., 1905, xiii. 436. T. B. OSBORNE and I. F. HARRIS. The Solubility of Globulin in Salt Solution. Amer. Journ. of Physiol., 1905, xiv. 151. H. C. HASLAM. The Separation of Proteids. Journ. of Physiol., 1905, xxxii. 267. R. H. A. PLIMMKU. The Formation of Prussia Acid by the Oxidation of Albumins. Journ. of Physiol., 1904, xxxi. 65 ; and 1905, xxxii. 51. P. A. LEVENE. The Cleavage Products of Proteoses. Journ. of Biolog. Chem., 1905-6, i. 45. E. R. POSNER and W. J. GIES. Is Protagon a Mechanical Mixture of Substances, or a definite Chemical Compound ? Journ. of Biolog. Chem., 1905-6, i. 59. H. D. DAKIN. The Oxidation of Amide-acids with the Production of Substances of Biological Importance. Journ. of Biolog. Chem., 1905-6, i. 171. A. E. TAYLOR. On the Synthesis of Protein through the Action of Trypsin. Journ. of Biolog. Chem., 1907, iii. 87. T. B. ROBERTSON. Note on the Synthesis of Protein through the Action of Trypsin. Journ. of Biolog. Chem., 1907, iii. 87. C. H. NEILSON. Further Evidence on the Similarity between Catalysis and Enzyme Action. Amer. Journ. of Physiol., 1905-6, xv. 148. C. H. NEILSON. The Inversion of Starch by Platinum Black. Amer. Journ. of Physiol., 1905-6, xv. 412. W. B. HARDY. Colloidal Solution. The Globulins. Journ. of Physiol., 1905-6, xxxiii. 251. R. H. A. PLIMMER and W. M. BAYLISS. The Separation of Phosphorus from Caseinogen by the Action of Enzymes and Alkali. Journ. of Physiol., 1905-6, xxxiii. 439. F. G. HOPKINS and E. G. WILLCOUK. The Importance of Individual Amino-acids in Metabolism. Journ. of Physiol., 1906-7, xxxv. 88. W. M. BAYLISS. Researches on the Nature of Enzyme Action. Journ. of Physio ., 1907-8, xxxvi. 221. i LIVING MATTEK 41 W. M. BAYLISS. The Nature of Enzyme Action. London, 1908. P. HARTLEY. On the Nature of the Fat contained in the Liver, Kidney, and Heart. Journ. of Physiol., 1907-8, xxxvi. 17. 0. ROSENHEIM and M. C. TEBB. The Non-existence of " Protagon " as a definite Chemical Compound. Journ. of Physiol, 1907-8, xxxvi. 1. H. D. DAKIX. Comparative Studies of the Mode of Oxidation of Phenyl Derivatives of Fatty Acids by the Animal Organism and by Hydrogen Peroxide. .lourn. of Biolog. Chem., 1908, iv. 419 ; and 1908-9, v. 173, 303. R. H. A. PLIMMER and F. H. SCOTT. The Distribution of Phospho-proteins in Tissues. Trans. Chem. Soc., 1908, xciii. 1699. A. E. TAYLOR. On the Synthesis of Protamin through Ferment Action. Journ. of Biolog. Chem., 1908-9, v. 381. A. E. TAYLOR. On the Composition and Derivation of Protamin. Journ. of Biolog. Chem., 1908-9, v. 389. T. B. ROBERTSON. On the Synthesis of Paranuclein through the Agency of Pepsin, etc., etc. Journ. of Biolog. Chem., 1908-9, v. 493. R. H. A. PLIMMER and F. H. SCOTT. The Transformations in the Phosphorus Compounds in the Hen's Egg during Development. Journ. of Physiol., 1909, xxxviii. 247. T. B. OSBORNE, LEAVEN WORTH and BRAUTLECHT. The Different Forms of Nitrogen in Proteins. Araer. Journ. of Physiol., 1908-9, xxiii. 180. R. H. A. PLIMMER and R. KAYA. The Distribution of Phospho-proteins in Tissues, Part II. Journ. of Physiol., 1909-10, xxxix. 45. E. V. McCoLLUM. Nuclein Synthesis in the Animal Bodv. Amer. Journ. of Physiol., 1909-10, xxv. 120. CHAPTER II LIVING MATTER: ITS FUNDAMENTAL PROPERTIES CONTENTS. Vital metabolism and phenomena of nutrition and reproduction. 2. Vital metabolism and phenomena of excitability and sensibility. 3. Laws of stability and variability of living species. Critical examination of Theory of Evolution ; Darwinism, and Neo-Lamarckism. 4. Evolutionary theories of Niigeli, Weismann, De Vries. 5. Distinctive characters of plants and animals : (a) Doc- trine of Linnaeus ; (b) doctrine of Ctivier ; (c) doctrine of J. R. Mayer, Dumas, Liebig. 6. Different forms of plant and animal metabolism: (a) Nitrifying bacteria ; (b) green plants ; (c) a-chlorophyllous plants ; (r/) herbivorous and carnivorous plants. Bibliography. THE fine morphological organisation and highly complex chemico- physical structure of elementary organisms, while sufficiently distinctive in character to differentiate non-living matter from living bodies, are not adequate to distinguish the living body from the dead, or from the products elaborated by the living. As a matter of fact, our knowledge of cytological structure depends mainly, and the data we possess in regard to the chemical composi- tion of the cell depend entirely, upon observations made on the dead organism. Yet it is upon the cytological and physico-chemical structure of the cell that the physiological activity and functions common to all living beings are founded, and it is by these that they are characteristically distinguished from non-living matter. General Physiology has of late undergone a remarkable development in the direction of philosophical interpretation. We must here confine ourselves to summarising the most definitely ascertained conclusions passing over the many hypotheses by which it is attempted to fill the unbridged gaps, and keeping strictly to what may serve as the foundation of scientific culture, and preparation to the study of human physiology. I. Life is essentially characterised by instability and movement, by the constant transformation of matter, with a corresponding evolution and accumulation of energy, which is exhibited in uni- cellular as in multicellular organisms, in plants as in animals. The name Metabolism (//cra/JoA-//, change) has been given to these physico-chemical changes of living protoplasm as a whole. It is 42 CHAP, ii LIVING MATTEK 43- the result of two opposite processes, which are continually super- posed and succeed each other : a synthetic, assimilative, and con- structive process, known as anabolism, and an analytical, dissiniila- tive, and destructive process, known as katabolism. In the anabolic process, the cell forms or elaborates organic matter from the nutrient materials, by the aid of energies derived from the environment or developed by oxidation of its own substance ; it takes up this organic matter by intussusception, transforms it into living protoplasm, or stores it as reserve material. In the katabolic process, the cell breaks up and uses the reserve materials, disintegrates its own protoplasm, and returns to the environment the products of decomposition, combustion, and activity. While the two opposite processes which constitute metabolism, or the exchanges of matter and energy, are intimately connected, they are differently distributed in the two principal phases of life, the progressive and the retrogressive. During the first phase the organism grows and develops, and is active in its functions; during the second, it dwindles and degenerates, and its functions are abated. The characteristic phenomena of nutrition, growth, and development in the organism are the natural consequences of metabolism, where the assimilatory or anabolic processes prepon- derate ; so, too, atrophy, senility, and death result from predomin- ance of the dissimilatory or katabolic processes, when life is on the wane. Between the progressive and retrogressive phases of life, between youth and age, there lies a long intermediate period, during which the two opposite processes, anabolic and katabolic, are practically in equilibrium. This is the phase of maturity, characterised by the full and vigorous exercise of all the vital functions, more particularly of the reproductive capacity. It is only when growth and ontogenic development are com- plete that the organism is able to reproduce itself. In other words, only when the factors or hereditary tendencies accumulated within the germ from which the organism has arisen, have become per- fectly developed and active, is it capable of forming by itself or by intercourse with an individual of the opposite sex, new germs, i.e. new aggregates of hereditary elements adapted for reproduction and conservation of the species. Metabolism is the invariable physiological basis of these marvellous phenomena : when the anabolic process predominates, the hereditary tendencies contained in the germ develop and become active ; when the evolution of the individual is com- plete, the metabolic process is turned to preparing the hereditary material of new organisms. II. Metabolism as the exchange of matter between organism 44 PHYSIOLOGY CHAP. and environment is intimately connected with metabolism as exchange of energy. Each living organism contains within itself at any given moment of its life a sum of potential energy, drawn from the sun's rays, and from the food-stuffs which it has ac- cuinulated or assimilated ; and this energy is always ready to discharge itself, or explode by transformation into kinetic energy, in consequence either of internal impulses or of external stimuli. The most striking form assumed by the energy developed in a living organism is the movement of masses, the power of surmount- ing resistance, i.e. of doing mechanical work. When these move- ments or changes of form or position in space depend upon internal stimuli they appear to be spontaneous or automatic, and are the most common and obvious objective sign that the organism that accomplishes them is living. When they are provoked by external stimuli they appear as reflex movements, i.e. as the effects of internal reactions to external stimuli ; in that case there is a striking disproportion between action and reaction, although this is not a distinctive sign of life, since the same may be observed in many chemical combinations the so-called explosives. What does, however, differentiate the latter from living substances, is that the chemical activity of explosives exhausts itself in the explosion, while the organism becomes fatigued with work, and recuperates in repose, i.e. at each reaction it only discharges part of its energy, and during the functional pauses it recovers by the anabolic process the quantity of potential energy that has been consumed. This peculiar capacity for developing, spending, and reaccum- ulating energy, which characterises living beings, has received the name of Excitability, and is distinguished as reflex or auto- matic, according as the reactions or excitations are provoked by internal tendencies or impulses, or by external stimuli, or excita- tions extrinsic to the organism. That there must be a marked analogy between the internal conditions of automatic, and those of reflex excitability, appears from the fact that it is often very difficult to differentiate objec- tively between automatic movements and reflexes ; on the other hand, many movements originally automatic become reflex by a simple morphological evolution of the elementary organism that produces them, while many originally reflex movements become automatic by long exercise and habit. These phenomena of excitability, which can be observed under various forms in all living organisms, are intimately connected with another group of phenomena, that can be directly observed upon ourselves alone, since they are accessible only to immediate internal observation or introspection. These last are the psychical phenomena, which as a whole constitute the content of con- sciousness. n LIVING MATTER The most rudimentary forms of consciousness, and as such the most widely dispersed (common, it may be, to all living beings), are represented by the phenomena of Sensibility, taken in the true psychological and not in the metaphorical sense which is invari- ably intended by physicists in speaking, e.y. of the sensibility of the balance, galvanometer, or thermopile. Certain physiologists, including Claude Bernard, have con- sidered sensibility to be the highest form, or evolutionary product, of excitability, i.e. of the physiological property common to all, even elementary, organisms of reacting to stimuli according to their nature. This, however, is either to disallow the psychical import of the word sensibility, or to admit as a fact that which is wholly inconceivable, i.e. the emergence of any psychical pheno- menon even in the form of vague internal sensations from simple molecular movements. According to our physiological concepts, sensibility and excitability do but express the same thing from two different standpoints. " Excitability is for us sensibilit// expressed in a verbal symbol suggested by external observation ; sensibility is the same excitability expressed in a verbal symbol derived from introspection. If we denote by excitation and sensation the effects corresponding, respectively, to excitability and sensibility, then excitation is the objective or material aspect of sensation ; sensation is the subjective or psychical aspect of excitation " (Luciani, 1892). This is merely a formal statement of the fundamental hypo- thesis of psychophysics, viz. that psychical phenomena are the correlatives of physiological phenomena, and express the aspects- under which the latter surge up in consciousness, and form its content. From the objective standpoint, psychical phenomena also must be regarded as so many forms of excitation, determined by the metabolism of the protoplasm, which is the common physio- logical basis of all vital phenomena. III. In fulfilling the functions of nutrition, reproduction, excitability, and sensibility, all plant and animal organisms are- subject to two laws, which to a certain extent are antagonistic, the Law of Heredity, and the Law of Variation. The first represents the principle of Stability, the second the principle of Evolution. Neither the one nor the other are to be understood in an absolute sense, since they are mutually exclusive, but it is extremely difficult to fix the precise limit between stability and variability, as appears from the history of biological science. Until some half-century ago the mind of most naturalists was dominated by the law of stability, Fixity of Species being a dogma, solemnly proclaimed by Linnaeus in his famous aphorism " Species tot sunt quot diversas formas ab initio produxit infinitum Ens" (Pliilosopkia botanica, 1751). A little more than a century later, in 1859, the publication of 46 PHYSIOLOGY CHAP. Darwin's book On the Origin of Species % Means of Nat-urul Selection caused a radical change in the ideas of the naturalists, and led to the almost unconditional triumph of the law of evolu- tion, to the detriment of the law of stability. The evolutionists fell into excesses, even denying the existence of biological species. We have recently entered upon a period of acute criticism of old and new theories of the Origin of Species, and at present the con- viction is gaining ground that none of these theories lias an -absolute demonstrative value, all having rather the significance of hypotheses that are of great use to the biologist in orientating himself in his positive researches. The idea of evolution has till now been the only conception imagined by the naturalists to account for the evident affinity exhibited among themselves by the different plants and animals which are grouped into species, genera, families, orders, classes. In all these groups a certain conformity of morphological type is apparent. According to the Evolutionary Theory, this unity of type is the expression of a unity of origin (monophyletic origin), irorn which the various families, genera, and species, animal and veget- able, have been derived by successive differentiations. Compara- tive anatomy, embryology, palaeontology, botanical and zoological geography, otter numerous facts that accord perfectly with the theory of evolution. With the progress of biological science, however, other data have gradually emerged that are difficult to reconcile with the concept of simple, continuous, monophyletic evolution. Many of the resemblances, analogies, and honiologies admitted by comparative anatomists up to a few years ago are no longer valid in face of a more profound and exact knowledge of the true structure and function of certain organs that were previously imperfectly known. For embryologists, the value of the so-called " great biogenic law " that was held by certain naturalists to be one of the fundamental proofs of evolution, has depreciated owing to the many exceptions which it presents. Further, the analogy between the development of the individual (ontogenesis) and the development of the species (phylogenesis) is essentially different, since the cell-ovum from which the individuals of the evolved species originate differs entirely from the ovum of the Protista, and must in itself (by a still incomprehensible mystery) contain the whole of the determinants of the complex final development, determinants that are obviously wanting in the ovum of Protista, or are contained there in a far less degree. Nor, again, have recent palaeontological data provided all the arguments in favour of the theory of evolution that were claimed a few years ago. Nowadays we can no longer invoke insufficiency of material to explain the great lacunae found in the development ii LIVING MATTER 47 of fossil plants or animals. Species, genera, families are seen to disappear incontinently, and other species, other genera, other families are substituted for them, with no evidence of that continuity and regularity of development which is demanded by the theory of evolution. Even when continuity of development is observed for any given organ (e.g. the foot of Solidungula), it is more apparent than real, since it has been arrived at by observing a single organ apart from all the other organs which constitute the species under consideration. Finally, it should not be forgotten that the fundamental basis for a complete and satisfactory theory of the evolution of the entire organic world, in virtue merely of the elements and forces of the inorganic world (as the pure evolutionists maintain with Spencer), is still wanting, viz. the demonstration of the spontaneous generation of life from inorganic matter and force. The greater the progress made by science, the more do the organisms believed to be simple appear complex, and the more improbable is spontaneous generation. Notwithstanding this and other serious difficulties, it must be admitted that the hypothesis of evolution has proved in practice to be a tool of remarkable utility. It has enabled us to gather up under one concept an infinite variety of scattered facts which would otherwise have escaped the researches and analysis of modern science, and thanks to which our positive knowledge has made extraordinary progress. Even if all biologists agree in admitting the theory of Evolu- tion, this harmony ceases when we attempt to determine its mechanism, i.e. its real causes and factors. The Darwinians and the so-called neo-Darwinians consider natural selection to be the principal, if not the sole factor in evolution, while the Lamarckians and the neo-Lamarckians almost entirely deny the value of selection, and assert on the contrary that transformation of species is the result of direct adaptation to the variable conditions of environment. Darwin and all his modern followers, while they defend the principle of selection to the hilt, are forced to admit an innate tendency to variation within the species, without being able to indicate its causes. If the said variation is slow, continuous, gradual and indefinite, as supposed by Darwin, this does not explain how the appearance of a variation can turn to the advan- tage of the species, and give opportunity for selection, in such a way as to favour the individual or individuals in which the new variation originates, in the struggle for existence, to the prejudice of the other individuals deprived of the same minimal variation. On the other hand, the concept of variability of species, both in plants and animals, has made considerable progress. In the time of Darwin a pure speculation, it is now a positive experi- 48 PHYSIOLOGY CHAP. mental fact ; and the new biometric methods have led to the discovery of facts and laws of capital importance which throw fresh light on the problem of the origin of species, showing it to be far more complex and difficult than had been supposed. These laws demonstrate the necessity of carefully distinguishing between variation and variation. Some variations are merely quantitative and fluctuating, and when studied by the statistical method are found to be subject to the so-called Law of Quetelet. Such variations are in strict relation with the nutritive conditions, or with the environmental conditions in general, and when these change, the values of the said variations change also, since they are not in themselves hereditary ; but the individuals that exhibit them return to the normal type whenever the conditions of the environment again become normal. It is clear that such variations can have no importance in determining a transmutation of species. Other variations, on the contrary, are qualitative and non- lluctuating, and are not subject to the Law of Quetelet. They are fixed, independent of the condition of the environment, and should in reality be termed not variations, but typical hereditary forms, or again elementary species (or races). Each of the classical Linnaean species comprises a greater or less number of such ele- mentary species, which in the first instance were confused with the fundamental typical species, and were erroneously held to be simple variations of the same. The majority of our plants and domestic animals are examples of these elementary species. Selection, as practised artificially by man, or effected by Nature in the struggle for existence, is of great importance in the sifting of such elementary species as are more suited to the needs of man, or better adapted to the environmental conditions. It would, however, be a great mistake to think that these elementary species were created and formed by means of selection. In reality selection did nothing more than seal and set in evidence what already existed in a mixed and confused state in the fundamental species, and it created nothing new. Hence the majority of the examples cited by Darwin from plants and domestic animals are of no value as evidence of the agency of selection in the formation of new species. It is on this account that many speak to-day of a crisis in Darwinism, when this means the theory of selection in a restricted sense, and is not a synonym of evolution. The falling-off in the supporters of Darwinism (in this limited sense) has reinforced the adherents of Lamarckism, who attribute the origin of species directly to the environment, to the action of external causes, climate, soil, nutrition, etc. According to Lamarck's original idea (1809), it is the want that creates the organ, which then becomes gradually perfected by use, while with disuse the organ atrophies and disappears. This idea presupposes ii LIVING MATTER 49 a teleological principle, regulating the transmutation and adapt- ability of the new organ, a principle in sharp contrast with the canons of the materialistic doctrine, which seeks for the mechanical causes of phenomena, and excludes all mystical, transcendental interpretations. The neo-Larnarckians renounce the teleological principle, on the strength of recently acquired data as to the determining action of certain external agents, e.g. light, heat, water, gravity, chemical substances, action of parasites, mechanical action (photomorphosis, therrnornorphosis, hydrornorphosis, geornor- phosis, chemomorphosis, biomorphosis, niechanomorphosis, etc.). This field of research, as cultivated especially by the modern botanist, is one of the most fruitful to the progress of biological science. At the same time it must be remembered that the external agent, e.g. light or heat, which determines a modification in the structure and conformation of an organ, is not the true cause of such a modification, but is rather the external stimulus adapted to develop a variation which already existed potentially in that organ. The determining agent, therefore, creates nothing new, it only stimulates the species to the expression of those properties which it already possesses potentially. This conclusion, which is- inevitable in the present state of our knowledge, must obviously limit to a great extent (some even say reduce to zero) the value of the direct action of external agents in the formation and trans- formation of species. But further : in order that the influence of the environment in the production of new characters in a species shall be efficacious and enduring, it is necessary to presuppose that the newly acquired characters are hereditary. Does any such heredity really exist ? This is one of the problems most keenly discussed among modern biologists. It is obvious that a decidedly negative reply would cause the whole edifice of the Lauiarckian and neo- Lamarckian theory to crumble. But no one is yet in a position to give a definite answer. The majority of the facts that were at one time cited in proof of the heredity of acquired characters have been triumphantly refuted by Weismann. Some few data relating to the lower organisms (Bacteria and Saccharomyces) remain, in which the heredity of newly acquired characters seems to be de- monstrated ; but how far these data are of value in the solution of the general problem with which modern biologists are so- engrossed, is a matter for discussion. For the present it must be confessed that with the exception of these few cases among the inferior organisms, all the attempts hitherto made to obtain new forms of plants and animals by the effect of one or several external causes have given negative results. IV. Starting from a profound criticism of Darwinism and Lamarckism, Nageli (1887) founded a new theory of evolution, VOL. i E SO PHYSIOLOGY CHAP. according to which the origin of species depends upon the intimate constitution of the germinal matter (or idioplasm}, inasmuch as this possesses an inherent tendency to perfect itself and to progress, developing by a slow and continuous evolution new and more complex forms, which are independent to a certain degree either of the variations of the environment or of the struggle for existence. It is undeniable that all the branches of the zoological trunk exhibit a progression from the lower forms to the higher, and always in a sufficiently cognate form, although the animals may be subjected to very different external conditions of existence and development. We see, for instance, that the eye, which in the rudimentary species of animals is represented by a simple spot of pigment, is provided in worms, in arthropods, in molluscs, in vertebrates, with accessory apparatus, such as the lens, the vitreous body, iris, choroid, etc. This tendency towards perfection, whether of single organs and apparatus, or of the individual as a whole, which is revealed everywhere in the organic world, must, according to Nageli (since it is comparatively independent of extrinsic vital conditions), find its explanation in the very being of the living- substance. Unlike Darwinism and Larnarckisin, which accord a pre- dominating importance to external causes in phylogenic evolution, Niigelism assigns the maximal importance to internal causes. Nageli's phylogenesis harmonises perfectly with his ontogenesis. The internal causes of the transformation are perfectly analogous to those by which the germ, or fertilised ovum, develops into the perfect individual, and the mutilated individual is capable of regenerating a missing member (e.g. a pollarded tree can recover all its branches, a lizard can reproduce its lost tail, a decapitated snail can reproduce its head). It is certainly within the intimate physico - chemical structure of the idioplasm of the egg, or mutilated individual, and not in the environment, that we must seek the determining cause of the individual development or reintegratiou. So likewise the determining causes of the mutability of species, and of the slow formation of new and ever more perfect species, must lie not in the environment, but in the intimate structure of the idioplasm. As in ontogenic evolution the environment, in addition to nutritive matters, provides a sum of stimuli favourable to the development of hereditary tendencies ; so in phylogenic evolution the environment provides impulses favourable to the development of creative tendencies, and in measure as these develop, moulds and modifies them, adapting them to the circumstances. It is not our task to follow Nageli in the development of his theory. From the standpoint of general physiology, it suffices to show that it harmonises perfectly with the principle we have II LIVING MATTER 51 formulated in regard to the elementary vital activities, which are all centred in metabolism. Both the reproductive capacity, by which the hereditary tendencies are rapidly completed, and the evolutionary capacity, by which the creative tendencies slowly develop, are founded upon the metabolic processes of living protoplasm. The same difference that we have seen to exist between automatic activity as depending essentially on internal impulses and tendencies, and reflex activity as due to external stimuli, exists between Nagelism and neo-Larnarckism. Starting from the psycho-physical theorem that conscious psychical phenomena are the introspective aspect of correlative physiological excitations, it is not too bold to assume that unconscious physiological phenomena likewise have a psychical aspect which is not clearly revealed to introspection, although it helps to build up the content of consciousness. With this premise, it seems reasonable to admit with Hering that ontogenic pheno- mena are the correlatives of an unconscious memory inherent in the protoplasm ; just as phylogenic phenomena might be considered the correlatives of an unconscious formative imagination. Weismann (in 1892) attempted a sort of reconciliation between Darwinism, Larnarckism, and Nagelism by assuming that the action of external causes might be fixed in the species, and become hereditary, if the said action were exercised on the plasma of the germinal cells. The modifications suffered by these would manifest themselves in the embryo and the adult individual, and would be transmitted to the descendants. In this way what Weismann calls germinal selection would become possible, in which the action of external agents, combined with natural selection, would deter- mine the origin of new species. These, however, are merely ingenious abstract speculations, which more or less successfully disguise our impotence to determine in any precise and accurate manner the relation between the action of external causes and the reaction of internal causes, manifested in the development of a morphological process. De Vries (1901) thought to escape from the many and insuperable difficulties of the hypotheses we have been examining by his Theory of Mutations, according to which new species originate not in a continuous variation, but in discontinuous variations, by sudden leaps which he termed mutations. In certain moments of the life of the species, under special conditions, some individuals may unexpectedly assume a series of new characters, differing from those possessed by their progenitors, and these characters might be hereditary. Many well-known facts in the history of plants and domestic animals seem to prove the sudden origin of new forms, as supposed 52 PHYSIOLOGY CHAP. by the theory of Be Vries. The majority of the new varieties cultivated in the fields, orchards, and gardens, when not obtained by hybridising, appear to have originated in such unexpected mutations. These facts were illustrated and described, even before De Vries, by Korschinski, who gave the phenomena the name of heteroyenesis. De Vries in his famous experiments at the Botanical Garden of Amsterdam saw several distinct species originate in a few years from Oenothera Lamarckiana -- Oenothera gigas, 0. albida, 0. rubrinervis, 0. nanella, etc., species which are said to give rise on direct fertilisation to products of a constant character. This would be the first experimental instance on record of neo-genesis in species belonging to the higher organisms. Not all biologists, however, are inclined to accept the conclusion of De Vries. Many (among them Bateson, and Cuboni in Italy) maintain that the so-called new species have no constant characters of descent, and that the new forms observed by the illustrious botanist of Amsterdam represent merely special cases of polyhybridism, in which the dominant and recessive elements of the progenital forms separate out according to Mendel's Law. In favour of this supposition we have the fact that some of the pollen grains of Oenothera Lamarckiana are deformed and sterile, as always occurs with hybrids. If we admit that the mutations observed by De Vries are no more than a return to the parent species, the fundamental basis of his theory loses all evidential value. Further, it is undeniable that many facts of systematic botany, and above all of palaeontol- ogy, can be more readily interpreted on the generally accepted theory of continuous variations. And lastly, it should be noted that De Vries himself recognises that the all-essential point, i.e. the internal causes of mutation, still remains an impenetrable mystery to human investigation. Whatever the future of the different theories relating to the mechanism by which the various living forms have developed one from another, whatever the nature of the internal causes deter- mining the formation of new species, it must never be forgotten that the Law of Descent, i.e. the general Theory of Evolution, which by means of Darwinism dominated the minds of scientific men for half a century, has been marvellously fecund, and has incited a vast series of researches, leading to the acquisition of new truths, which without that theory might never have been gathered up. It therefore remains the corner-stone of biological research ; even more than as a hypothesis we are constrained to admit it as a necessary postulate, because its negation would logically include the negation of a unitary biological science. From the foregoing observations on the vital activities common ii LIVING MATTEE 53 to all living beings, we may formulate the following general propositions : (a) All vital activity is founded on the metabolism of living matter. (6) As a material exchange, metabolism expresses itself in anabolic and katabolic processes. (c) As a dynamic exchange, metabolism manifests itself by the accumulation and discharge of energy. (cT) The anabolic and katabolic processes express themselves in the phenomena of nutrition (consumption and repair) and reproduction (formation and evolution of germs). () The accumulation and transformation of energy is exhibited in the phenomena of rest and excitation (automatic or reflex in character). (/) All the processes of vital metabolism conform to the conservative laws of heredity, and to the evolutionary laws of variability. ( PHYSIOLOGY CHAP. pensable to life. Some animals have adapted themselves to a purely protein diet, and, further, to a single form of the same. Thus, e.t/., the clothes-moth lives exclusively on the keratin of which the hairs of the wool or fur consist, and from which it derives all that is necessary for the construction of its protoplasm. Again, as we shall see, it is possible to keep a dog alive, and in its normal state, on a purely flesh diet, while this is found impossible on an exclusive diet of fats and carbohydrates, no matter how abundant. The chief part of the mineral substances which enter into the chemical composition of animals cannot be assimilated as such, but only when they are present in organic combinations, as, e.g., the calcium phosphate of milk casein, the potassium salts of muscle protein. If mice are fed on casein from which the greater part of the salts contained in the organic combinations of milk have been previously washed out, and if sugar be added, as well as all the salts contained in the ashes of milk in a non-organic form, the mice perish slowly during this diet, and succumb after about forty days (Lunin). This and similar experiments on artificial feeding in other animals, show that they are only capable to a small extent of assimilating inorganic substances, i.e. of binding them synthetically into the protein molecule on which the living protoplasm is nourished. BIBLIOGRAPHY The following may be consulted for the literature of the Theory of Evolution : LAMARCK. Philosophic zoologique. Paris, 1809. CHARLES DARWIN. On the Origin of Species by Means of Natural Selection. London, 1859. C. VON NAGELI. Meehanisch-physiologische Theorie der Abstammungslehre. 1884. WEISMANN. Das Keimplasnie : eine Theorie d. Vererbung. Jena, 1892. H. DE VRIES. Die Mutationstheorie. Leipzig, 1901, 1903. YVES DELAGE. L'Heredite et les grands problemes de la biologic eerie rale. Paris, 1903. DETTO. Die Theorie d. direkten Anpassung. Jena, 1904. PAULY. Darwinismus und Lamarckismus. Munich, 1905. LOTSY. Vorlesimgen liber Deszendenztheoricn. Jena, 1906. SCHNEIDER. Einfuhrung in die Deszendenztheorie. Jena, 1906. RIGNANO. Sur la transmissibiliti' des caracteres acquis. Paris, 1906. The two following text-books may be consulted for the general physiology of plants, and their characteristics as distinct from animals : E. STRASBURGER, F. NOLL, H. SCHENCK, A. F. W. SCHIMPER. Lehrbuch d. Botanik. Jena. G. Fischer, 5th ed., 1902. W. PFEFFER. Lehrbuch d. Prlanzenphysiologie. Leipzig, 1897-1901. Recent English Literature of the subject : W. PFEFFER. The Nature and Significance of Functional Metabolism in the Plant. Proc. Roy. Soc., London, 1898, Ixiii. 93. K. PEARSON. Data for the Problem of Evolution in Man. Proc. Roy. Soc., London, 1900, Ixvi. 23, 316. K. PEARSON. Mathematical Contributions to the Theory of Evolution. Proc. Roy. Soc., London, 1900, Ixvi. 140. ii LIVING MATTEE 63 ~\V. BATESON. Heredity, Differentiation, and other Conceptions of Biology. Pw. Roy. Soc., 1901, Ixix. 193. T. M. BALDWIN. Development and Evolution. London & New York, 1902. A. K. MARSHALL, E. B. POULTON, etc. Five Years' Observations and Experiments (1896-1901) on the Bionomics of South Africa Insects. Trans. Entom. Soc., London, 1902, p. 287. }\. PEARSON. Mathematical Contributions to the Theory of Evolution. Proc. Rov. Soc., London, 1902, Ixix. 330 ; 1903, Ixxi. 288. A. R. WALLACE. Darwinism : Exposition of the Theory of Natural Selection with some of its Applications. London, Macmillan. 1902. \V. F. R. WELDOX. Professor de Yries on the Origin of Species. Biometrika, 1902, i. 365. TH. M. MORGAN. Evolution and Adaptation. New York, 1903. \V. BATESON. Opening Address at the British Association (Zoology). Nature, 1904, Ixx. -106, 539. A. D. DARBISHIRE. On the bearing of Mendelian Principles of Heredity on Current Theories on the Origin of Species. Manchester Lit. Phil. Soc., 1904, xlviii. A. S. PACKARD. The Origin of the Markings of Organisms (poecilogenesis) due to the Physical rather than to the Biological Environment ; with criticism of the Bates-Miiller hypotheses. Proc. Amer. Phil. Soc., 1904, xl. 393. R. C. PUNNETT. Merism and Sex in spinax niyer. Biometrika, 1904, iii. Part IV., p. 313. A. E. BROWN. The Utility Principle in Relation to Specific Characters. Proc. Ac. Nat. Sc., Philad., 1905, Ivii. 206. E. S. CONKLIN. The Mutation Theory from the Standpoint of Cytology. Sc., N.S., 1905, xxi. 525. H. E. CRAMPTON. On a General Theory of Adaptation and Selection. Journ. of Exper. Zool., 1905, ii. 425. C. B. DAVENPORT. Evolution without Mutation. Jouru. of Exper. Zool., 1905 ii. 137. W. S. HARWOOD. New Creations in Plant Life : an Account of the Life and "Work of Luther Burbank. New York, 1905. N. DE VKIES. Species and Varieties. Chicago, Open Court, 1905. R. H. LOCK. Recent Progress in the Study of Variation, Heredity, and Evolution. London, 1906, xv. 299 pp. . U. MERRIAM. Is Mutation a Factor in the Evolution of the High Vertebrates ? Science, 1906, p. 241. CHAPTEK III LIVING MATTER: CONDITIONS BY WHICH IT is DETERMINED CONTENTS. 1. Nutrition the necessary external condition of vital metabolism. Phenomena of inanition. 2. Importance of water. Latent life and anabiosis. '6. Importance of oxygen. Aerobic and anaerobic life. 4. External temperature indispensable to life. 5. Total pressure of air and water, and partial pressure of oxygen and carbonic acid. 6. External stimuli. 7. Chemical stimuli. Cheino- taxis. 8. Mechanical stimuli. Barotaxis. 9. Thermal stimuli : thermotaxis. 10. Photic stimuli. Phototaxis and Heliotaxis. 11. Electrical stimuli. Galvano- taxis. 12. The various biological zones of ocean life (Plankton). 13. Internal conditions and stimuli of metabolism. Theory of automatism. 14. Hypotheses to explain the intimate mechanism of living matter. Bibliography. Two orders of conditions, external and internal, are essential to the maintenance of metabolism. Both the one and the other may act directly or indirectly. The former cannot fail without cessation of life, nor the latter without modifications and disturbances of vital phenomena. If we were acquainted with all the internal and external conditions of life, the task of Physiology would be terminated ; the " conditioned," i.e. Life, would be perfectly known to us. Not all the vital conditions are essential in the same degree to- every living being. Each organism has special requirements in virtue of which it lives and nourishes. Each living species, there- fore, demands special treatment. From the standpoint of general physiology we have only to consider in broad outlines the most universal and best known of the vital conditions. I. The first and most general external condition of metabolism is Nutrition, i.e. the sum of the chemical materials essential to the building-up of living protoplasm. We saw in the last chapter how various were the chemical forms of the foods necessary to different groups of living beings to nitrifying bacteria, green plants, saprophytic and parasitic fungi, herbivorous and carnivorous animals. To this we may add that in accordance with the chemical composition of the nutritive medium, the various elementary organisms react very differently. Some can only live iu fresh water ; others in salt water. All die more or less rapidly when brought into distilled water. Every 64 CHAP, in LIVING MATTER 65 simple or complex organism, indeed, exhibits a certain capacity of adapting itself to an environment and nutrition different from those to which it has been accustomed, provided only that the change is effected very slowly and gradually. In consequence of this adaptation, temporary modifications of the specific characters ensue. According, however, to certain experiments of Nageli, these are not persistent, but quickly disappear when the organism is brought back to its original environment and alimentation. In order to form an adequate concept of the adaptability of various organisms to unusual conditions in respect of nutrition, we may refer to certain bacteria, recently investigated by Winogradsky, which he calls sulphur or iron bacteria. The sulphur bacteria are represented by a family of microbes, which can only live in the water of bogs or marshes, where, owing to the decomposition of vegetable and animal matters, there is a great development of hydrogen sulphide. This they absorb, oxidising it, and setting free the sulphur, which they accumulate in the body of their cells in the form of highly refractive granules. On subsequent oxidation, these granules give rise to a formation of sulphuric acid, which is excreted as such. The iron bacteria live in marshy water, where ferrous carbonate is found in solution ; this they take up, and convert it into ferric carbonate, which readily decomposes on excretion, and the precipitate of iron oxide forms the ochre -like deposit known as meadow-ore. Both sulphur and iron bacteria perish when brought into spring water, which contains no hydrogen sulphide or ferrous carbonate, while these compounds act as poisons to all other living- beings. They must, therefore, have undergone a permanent adapta- tion to a quite exceptional form of environment and nutrition. Whatever the nature of the food-stuffs appropriate to the various organisms, they are indispensable to the maintenance of life. Absolute or relative deprivation of food produces a state of inanition, during which the organism primarily consumes the reserve materials stored up in the body of the cell, and then absorbs its own protoplasm, shrinking more and more, until it finally perishes when the protoplasm has no longer enough potential energy to maintain the balance of metabolism (Fig. 17). v^- IT. - , . , . . , , ,. . , ,. ciliated infusorium. (Jensen.) a, The individual living elements ot under normal COI1( iitions ; &, in which the tissues and organs of the S^*Sj l ?a tt d J higher animals are composed draw all pnved of granules. Magnification, . , a j -liO diameters. their nourishment from a common fluid, the lymph, which circulates in the interstices of the tissues. During inanition, the total consumption of the organism is not VOL. i F (Jti PHYSIOLOGY ..-HAP. equally distributed among the different tissues; a sort of struggle for existence goes on between them, some being consumed and liquefied for the benefit of others, which continue to exist as parasites, and are even able to reproduce themselves (Luciani). The process of inanition in the higher animals and man will, however, be treated in detail later on. II. Another condition no less indispensable to metabolism is water, which infiltrates the living protoplasm in large quantities, rendering it soft or semi-fluid. In order to realise the importance of water to the vital functions, we need only consider the consequences of natural or artificial desiccation in unicellular organisms. Within certain limits the intensity of metabolism increases or decreases with the increase or decrease of the water content of the living matter, while beyond those limits vital activity ceases altogether. In the great majority of plants, natural dryness of environment is sufficient to cause death. Many mosses, lichens and algae, however, which live on naked rocks are able to support the drought of summer without injury. Seeds and spores, in particular, when removed from the plant, may be kept in a dry state without losing their capacity for germination. It was formerly stated that the wheat found with the Egyptian mummies retained its power of germinating after more than two thousand years; but this fact was disproved by the famous Egypto- logist Mariette. It has, however, been demonstrated that spores of mosses and the seeds of Mimosae, kept in a dry state for over sixty years in a herbarium, were perfectly capable of germination ; other seeds, on the contrary, lose their vitality after one year, others again after a few days, while others will not tolerate any desiccation, e.g. the seeds of Salix. Some groups of animals can be kept for years in a desiccated state without losing the faculty of awakening to life a few moments after they are moistened again (Prayer's anabiosis). Among these are the so-called Roti/erae, small crustaceans, and the Tardegrada, arachnoids resembling mites, which live in the moss and dust of roofs, as discovered by Leeuwenhoek (1719), who first described this remarkable phenomenon. Also the Anguillulae of mildewed wheat, on which Spallanzani (1776) made many curious experiments of repeated anabiosis. Lastly, the greater part of the bacteria, particularly in the spore state, come under the same category. It is not easy in any of these cases of apparent death to determine whether there is absolute suspension of metabolism, a true latent or potential life, or a metabolism reduced to the lowest terms, i.e. to the state which Spallauzani was the first to characterise as minimal life. To decide the question, it is neces- sary to determine whether these organisms in a state of apparent death exhibit any trace of respiratory exchange, i.e. of absorption Ill LIVING MATTER 07 of oxygen and excretion of CO.,. W. Kochs (1892) used for this purpose a large quantity of perfectly dry seeds of plants, which he placed in large glass tubes from which the air had been pumped out, and which were then hermetically sealed. After many months, a minute analysis of the contents of the tubes failed to detect any trace of carbonic acid ; and yet the seeds perfectly retained their capacity for germination. This experiment proves that it is possible to establish a state of true potential life in the seeds of certain plants. The results of a number of experiments undertaken by the author in collaboration with Piutti (1888) on silk-worm eggs were somewhat different. Without artificial desiccation these, did not entirely cease to breathe when kept for a long while at a temperature of C., and even at that temperature they could not survive prolonged exposure to an atmosphere of pure nitrogen. When kept for 139 days in conical flasks in which the air was maintained constantly dry by means of concentrated sulphuric acid, they perished entirely if the temperature was 9-14 C., and partly if it was C. It is therefore clear that under these conditions the silk- worm eggs are reduced to a state of vita minima. When placed in glass flasks, in which a perfect vacuum was produced by the mercury pump, after which they were sealed up and kept at C., more than half the eggs after 83 days were alive, and capable of development when brought under normal conditions of incubation. Here we have evidently a state of minimal life approximating to that of latent life. Lastly, the silk-worm eggs were placed under a glass bell-jar, hermetically sealed to a plate and containing a desiccator with concentrated sulphuric acid ; when after 128 days the enclosed eggs (which had shrunk in an extraordinary way from the desiccation) hatched out, a very copious but incomplete brood of caterpillars was produced, which were smaller and less lively than the normal. From these results it seems probable that insect eggs, like plant seeds, can be artificially brought by desiccation into the state of latent or potential life. According to Preyer's ingenious comparison, this state is comparable to that of a clock wound up, but with the pendulum arrested ; the state of death, on the contrary, is like a clock which can no longer go because its wheels are broken. III. We saw in the last chapter that plants breathe like animals, i.e. they take in oxygen, in order by a slow process of combustion to form carbonic acid and water. The presence of oxygen is, accordingly, one of the most fundamental conditions in the active upkeep of metabolism. This does not mean that the presence of oxygen as such is indispensable to the maintenance of life. In order to under- stand its importance we must start with certain general con- siderations. 68 PHYSIOLOGY CHAP. Every assimilatory or anabolic process results iu an accumu- lation of energy, and necessarily implies a source of kinetic, which can be transformed into potential, energy. Each dissimilatory or katabolic process, on the other hand, results in a dispersion of energy, and presupposes a store of potential, to be transformed into kinetic, energy. This is why the two opposite processes are simultaneous, or constantly and rapidly alternating, during life, while the two together constitute metabolism, which as we have seen is the physiological basis of all the phenomena of life. Since in green plants anabolic largely predominate over katabolic processes, the energy which they develop by oxidation is inadequate for the synthetic formation of their highly complex organic substances, and the intervention of the energy derived from the sun's rays becomes necessary. In animals, on the contrary, in which katabolic processes largely predominate, the energy which they develop by the oxidation of organic substances is not only enough to ; yield mechanical work, and to keep the temperature of the body above that of the environment, but also suffices to secure the anabolic processes, or new organic syntheses, by elaboration of the food- stuffs drawn from plants. The destruction of the organic molecules by the katabolic pro- cesses does not take place all at once, so as immediately to turn combustible substances into final products ; but it is effected gradually and successively, the more complex being converted into other less complex molecules, and these into the end-products rejected by the body. The presence of oxygen is not essential to all these regressive metamorphoses. In the absence of free oxygen, protoplasm is able for a certain time to obtain oxygen from the combinations in which it is held loosely or firmly, and thus to develop kinetic energy. The great plasinodia of the Myxomycetes, e.g., if placed in a medium deprived of oxygen, will continue their movements for three hours ; ciliated epithelia can live even longer without oxygen (Engelmaun) ; excised frog's muscle placed in an atmosphere of pure hydrogen will give off carbonic acid for many hours before it becomes inexcitable (Hermann). Many organisms of the lowest orders, particularly in the numerous groups of bacteria, have the faculty of living permanently without oxygen. Pasteur, who was the first to call attention to this most important phenomenon, gave the name of anaerobic to the organisms which live in the absence of oxygen, in contradistinction from the aerobic, which can only live in presence of this gas. According to Tarozzi (1905), the incapacity of anaerobic bacteria to develop in culture media in the presence of oxygen, is due not to a toxic action of the oxygen on these microbes (as has been stated by many authors) but rather to chemical modifications of the proteins in the broth used for the in LIVING MATTER 69 culture. These modifications consist essentially in processes of oxidation, and the anaerobes appear to he incapable of utilising highly oxidised proteins in their assimilation. Accordingly, they can only develop when these substances are once more reduced, which is effected either by artificially removing the oxygen, or (after Tarozzi) by adding to the broth a scrap of fresh organ aseptically prepared, which acts as a reducer, in virtue of the chemical processes of which it is the seat, and favours the develop- ment of the anaerobes. In this case it is not necessary to remove the oxygen before the bacteria can develop. This explains how such development takes place naturally when these bacteria are in the presence of tissues of animals that have just died, or, generally speaking, whenever they find protein matters at their disposal which have not suffered profound oxidative changes. And this is why all anaerobes belong exclusively to the class of putrefaction microbes (saprophytes). According to the work of Duclaux, Gautier, and Ehrlich, anaerobic metabolism may be recognised not only in a great number of microbes, but in a still greater number of plant and animal cells. Many decompositions of organic molecules due to enzyme action within the cell, or in external secretions, are produced without intervention of atmospheric oxygen, and are accompanied by a development of energy which is partly utilised by the cells for their constructions or organic syntheses. Thus, e.g., the katabolic action of beer yeast, in the absence of oxygen, breaks up glucose into alcohol and carbonic acid, with evolution of heat which is partly employed in the multiplication of the cells of the ferment. In a well-aerated medium the same beer yeast, on the contrary, effects complete oxidation of the molecule of glucose, converting it into water and carbonic acid, and in this case there is a greater development of heat and a far larger multiplication of Saccharo- ini/ces. Pasteur's interpretation of these phenomena is very illuminating : Saccharomyces, in order to nourish and reproduce itself, makes great use of the energy developed in the oxidation of sugar, when it is in an oxygenated medium. When oxygen is scarce, it utilises the inferior amount of energy which it is able to develop by abstracting oxygen from the fermentable material, i.e. from the same sugar, by a kind of internal oxidation. Accordingly, it is not oxygen as such that is essential to life, but the energy that is developed by any kind of oxidation. Green plants have less need of oxygen than animals, because they obtain from the sun's rays a great part of the energy which they require in fixing the carbon. If the majority of living beings positively demand free oxygen, it is because much heat is developed in its combinations, which can be utilised in a variety of ways. In proof of the extent to which oxygen is essential to the life 70 PHYSIOLOGY CHAP. of the various tissues of the higher animals, we may refer to a remarkable experiment of Pfliiger's on the frog. He placed two of these animals in an atmosphere at C. which had scrupulously been deprived of every trace of oxygen. After a quarter of an hour they exhibited considerable dyspnoea, which, however, was unaccompanied with convulsions. After live hours the frogs were quiet and flaccid, but reacted to stimulation with a wire. After nineteen hours they lay as if dead, and no longer reacted to tin- strongest cutaneous stimuli, or showed any trace of respiratory movement. After twenty hours, they were taken out of their prison into the fresh air, but no sign of life could be elicited in spite of repeated insufflation of air through the trachea. On opening the thorax of one of the frogs, Pfliiger was astonished to see the heart still beating with great energy, while the arteries contained bright red blood. But it was not till two hours after the animal had been brought into the oxygenated atmo- sphere that spontaneous muscular movements were exhibited, followed by reflex movements and spontaneous respiration. The more complicated voluntary movements, how r ever, which depend upon the higher nervous system never came back. To explain this long survival in an atmosphere wholly deprived of oxygen, it must be admitted for vertebrates also that the living- protoplasm of the various tissues has the property (in different degrees) of utilising the oxygen which is bound up in the organic molecules. The cells of the central nervous system are the most sensitive to deprivation of free oxygen ; other cells, on the contrary, can live for a long while in a medium destitute of oxygen, because they have the power of taking it from organic combinations, and utilising the potential energy. The most interesting phenomenon, from the point of view of anaerobic metabolism, is afforded by the group of bacteria which are not only capable of living in the absence of oxygen, but die in a medium that contains it, e.g. Tetanus and Anthrax bacilli. Interesting phenomena, too, are exhibited by other bacteria, e.g. the comma bacillus of Cholera, which is greedy of oxygen, and is at the same time capable of living and multiplying enormously in the intestine, where there is no trace of free oxygen, so that it must necessarily utilise the combined oxygen of the alkaline salts. IY. In addition to food - stuffs, water and oxygen, which penetrate into the body, and directly condition metabolism, other conditions of a dynamic character are indispensable in order that the vital functions may be accomplished. The external temperature exercises a predominant influence on elemen- tary organisms. Each cell demands a temperature oscillating between given limits, beyond which the cell must die. For the majority of plant and animal cells, the maximal limit of endurable temperature lies between 40 and 4T C. Kiilme found that the in LIVING MATTER 71 contractile protoplasm of Amoebae coagulated sometimes at 40 C., sometimes at 45 C. For plant cells, Max Schultze found that the fatal temperature could be raised to 47" C. Other elementary organisms, indeed, support much higher temperatures, which would seem incredible if they were not substantiated by direct measure- ment. In the hot baths of Oasarnicciola, e.g., certain Algae nourish at a temperature of 03 C'., while, according to Ehrenberg, some of the ciliated Infusoria (Occillaria or JRotifera) can live at a temperature of 81 - 85 C. More surprising still, the spores of Anthrax, according to Koch, Brefeld and others, can support a temperature of over 100 C.,and only lose their vitality completely after three hours' dry heat at 140 C. It must be remembered in explanation that the protoplasm of these organisms consists of proteins combined in such a way that they do not coagulate nor decompose at these high temperatures. The minimum temperature compatible with life is equally surprising. While as a rule the poikilothermic animals and plants die when the temperature falls to such a point that the water imbibed by the protoplasm freezes, Raoul Pictet's latest experi- ments show that a temperature of less than C. is not necessarily fatal to certain organisms. In fact he ascertained positively that fishes frozen at a temperature of - 15 C. can recover their vitality, provided the thawing is effected with great caution. If, however, the fall in temperature amounts to - 20 C., they inevitably perish. Frogs, .on the contrary, tolerate a temperature of - 28 C., centipedes one of - 50 C., while, lastly, bacteria can survive exposure to - 100 C. Here we reach the vexed question whether frozen animals, capable of recovering their vitality on thawing, are in a state of minimal or of absolute latent vitality. Although the latter possibility is not excluded, Pictet's experiments do not seem to favour this hypothesis. If these frozen fishes were in a condition of latent vitality, it is difficult to see why they should not be indifferent to a fall of temperature below - 15 C., which they can survive. It seems more rational to admit that at this temperature metabolic exchanges are still maintained, although reduced to the lowest terms, and that death ensues when metabolism ceases altogether. V. The pressure of the air and water in which these organisms live must also be considered among the general conditions of life. It is indeed evident a priori that pressure must act against the thermal vibrations of the atoms ; when therefore there is a marked rise of pressure obstructing the thermal vibrations, this favours the appearance of chemical combinations, while a marked diminu- tion, by increasing the amplitude of the said vibrations, must weaken the mutual attraction of the atoms and dissociate the unstable chemical combinations. PHYSIOLOGY CHAP. Very little work has been done on the determination of the limits between which the total pressure of the air and water, and the partial pressure of the oxygen and carbonic acid which these contain, condition the life of the organisms which inhabit them. The experiments of Paul Bert (1873) bring out the interesting fact that pure oxygen under a pressure of three atmospheres is fatal to warm-blooded animals, while ordinary air only produces the same effect at a pressure of 15-20 atmospheres. The same fatal effect ensues when the partial pressure of the oxygen of the air is reduced below a certain limit. In order to determine how great a fall in the barometric pressure is compatible with life, we may utilise certain data furnished not so much by ascents of the highest mountains as from aerostatic ascents, in which the effects of fall of barometric pressure are not complicated by muscular fatigue. The famous ascent by Croce-Spinelli, Sivel, and Tissaudier in 1875 was fatal to the two former. When the balloon reached 8000 metres Tissaudier, the sole survivor, lost consciousness, and only came to his senses when the balloon had dropped to 7059 metres. We know hardly anything of the effect of aqueous pressures upon sea animals. Contrary to former conceptions, it has within the last few decades been ascertained that there exists a special flora and fauna at the lowest depths of the ocean, in regions where there is a pressure of several hundred atmospheres, and where no light can ever penetrate. The fishes caught at the greatest depths are, when first brought to the surface, so distended in consequence of the sudden reduction of pressure, which allows the gases in their bladder to expand, that the viscera protrude from their mouths and the scales stand up (Keller). In regard to the pressure exerted by water upon marine animals, the fact must be insisted on that it exercises a great influence only upon such organs as, like the fish's swim-bladder, contain gas in the gaseous state, and do not communicate with the exterior. The tissues of these animals, which may be considered as liquids, only feel the effects of the high pressure in a negligible degree, since, as we know from physics, several hundredths of atmospheric pressure are necessary in order to obtain any marked diminution in volume of fluids these being practically incom- pressible. This is confirmed by the fact that marine animals, such as Echinoderrns, Molluscs, Crabs, and Selachians or Teleosteans, which have no swim-bladder, and normally live at a great pelagic depth, can be transported to the surface without any danger, and continue to live for a long time in ordinary aquaria when the pressure of the water is from i-1 metre. VI. With the exception of those above enumerated, none of the general external conditions are essential to life. Other external physical or chemical factors may indeed influence vital in LIVING MATTER 73 metabolism to such a marked degree so as to render them indispensable to the life of given groups of organisms, e.g. light in the case of green plants. These special external conditions are usually known as stimuli, since they exert a direct influence on the excitability of the protoplasm as expressed in the various forms of excitation. In the previous chapter we distinguished between automatic and reflex excitation ; the former being determined by internal, the latter by external stimuli. This must not be understood to mean that the excitations which have the character of spontaneity, as opposed to the reflexes provoked from without, are independent of all external determining factors. The first, like the second, are effected under the constant influence of the general and normal external conditions of life ; but while automatic excitations have for their immediate and determining cause a stimulus or impulse proceeding from the living matter itself, reflex excitations have for their immediate and determining cause either a sudden change in the normal external conditions, or the abrupt and unexpected intervention of other special external agents. The external agents that commonly function as stimuli are represented by different chemical actions, by various mechanical shocks, by light, heat, and electricity. The changes in metabolism determined by the action of stimulating agents may be predominatingly anabolic or katabolic in character. In the first case there is development of kinetic energy, and the phenomena are those of excitation properly so- called ; in the second, there is an accumulation of potential energy, and the phenomena are said to be assimilatory. or trophic, or inhibitory, according to the most conspicuous characteristic which they present under observation. When the action of the stimuli is too prolonged, or too frequently repeated, or exceeds the physiological limits in its intensity, there may result not an increase but a depression, suspension, or abolition of metabolism, as exhibited in the phenomena of fatigue, paralysis, or death of the protoplasm. We must now briefly summarise the most universal and best ascertained conclusions in each of these categories of phenomena. VII. Innumerable chemical compounds function as stimuli when brought into relation with living matter, i.e. they provoke phenomena of excitation. The mode in which they act has, how- ever, been experimentally studied only in a very few cases. We must therefore confine ourselves to recording certain typical phenomena which are particularly worthy of attention. Max Schultze (1863) and Kiilme (1864) made classical re- searches on the effect of chemical stimuli upon the amoeboid movements of masses of naked protoplasm, such as the Rhizopoda (Amoebae, Myxomycetes, Poly thai amidae, etc.). The effect most 74 PHYSIOLOGY CHAI'. generally observed was contraction, i.e. retraction of the pseudo- podia. The most various chemical substances are capable of producing this effect: 1-2 per cent solution of sodium chloride, dilute hydrochloric acid O'l per cent, caustic potash 1 per cent, weak solutions of other acids, alkalies, or salts. The Rhizopods treated with these solutions assume a globular form on retracting their pseudopodia, owing to the concentric contraction of the protoplasm (Fig. 18). Ciliated cells, on the contrary, when treated with the same stimuli, increase their vibratile movements sometimes to a very marked extent. Smooth and striated muscles contract, and sometimes exhibit a rhythm of contraction that they do not normally possess, recalling the rhythmical movements of the vibratile cilia. Besides the contractile effects of chemical stimulation, it is FK.. 1*. Ai-tiiiiixiihuei-iiiiii l-^i-ltlnii-nii. (\Vnvoru.) c, under normal conditions ; //, at commence- ment of chemical excitation, the filiform pseudopodia are contracted and varicosi- ; <, after prolonged chemical excitation, the pseudopodia are completely retracted. possible also to observe expansive effects, i.e. active elongation of the pseudopodia in Amoebae, Myxomycetes, etc., effects which in the first instance were studied by Kiihne. On placing an amoeba, for instance, in a gas chamber in which oxygen has been substituted for hydrogen, the movements are suspended after a short time. On again admitting oxygen, the amoebae, after twenty-four hours of inactivity, at once begin to expand their pseudopodia with normal vivacity. Even more important than this direct excitation are the phenomena of the directive action of chemical stimuli upon the movements of elementary organisms, phenomena known as cheino- tactic or chemotropic. Cheinotaxis, as first discovered by Engelmauu on Bacteria, observed by Stahl on Myxomycetes, and studied on a large scale by the botanist Pfeffer in 1887, has assumed a great) importance. Positive must be distinguished from negative chemotaxis. The Ill LIVING MATTEE former consists in the active approach of the micro-organisms to the source of the chemical stimulus, as if attracted by it ; the second consists in the opposite phenom- enon, i.e. active withdrawal from the seat of the stimulus, as if it exerted some repulsive action. A given solution may be an energetic chemotactic stimulus for one organism, and weak 'for another. The efficiency of the stimulus depends on its chemical constitution ; potash, e.g., is active in combination with one acid and not with another. Certain poisons (sodium salicyl- ate, morphia) in weak solutions exert an attractive action, in concentrated forms a repulsive action. Some substances (alcohol, alkalies, free acids) always have a repellent action, i.e. they exert negative chemotaxis. The method adopted by Pfeffer in studying chemotaxis is very simple : he merely immerses in the water which con- tains the microbes a capillary glass tube filled with the solution to be investigated, and closed at one end. If the microbes penetrate into the tube, there is positive chemotaxis ; if they move away, there is negative chemotaxis. If, e.g., a O'Oo per- cent solution of malic acid is introduced into the capillary tube, the open end of which dips into a drop of fluid containing the spermatozoids of Ferns, the malic acid will scarcely have begun to diffuse in the drop when the spermatozoids move towards the entrance of the tube and crowd into it. The same thing may be seen with a much weaker solution (O'OOl per cent) of malic acid. The movements of the sper- matozoids must be directed by the differ- ence in concentration of the acid which is in contact with the different parts of their body. When the concentration of the acid diffused in the drop becomes the same at every point, it can no longer exercise any directive action upon the movements of the sper- matozoids. Leber, Massart and Bordet, Metschnikoff and others discovered FIG. 1'.'. Positive chemotaxis of" leucocytes in presence of Xhi-ph//- loeoecuspyogi ueti'liius. (Massart.) Capillary glass tube (magnified under the microscope), closed at one end, and filled \\ith a culture of Staphylococcus, to- wards which the leucocytes are streaming through the open end of the tube. The observa- tion is made after the capil- lary tube lias been introduced into the peritoneal cavity of the frog, or beneath the skin of a rabbit, ami kept there IO-V-! hours. 76 PHYSIOLOGY CHAP. cheinotactic activity in the leucocytes of vertebrate blood. The products of the metabolism of pathogenic bacteria exert a marked chemotactic action upon them (Fig. 19), a fact which is of great importance in the interpretation of the inflammatory phenomena of infective diseases, as we shall see in discussing Blood. VIII. Mechanical stimuli (blow, contact, puncture, shake, pressure, etc.) are the simplest means of provoking excitation in living matter. The least shake of the object- carrier on which the movements of an amoeba are being watched under the microscope is sufficient to produce temporary standstill, and if the impact is strong enough a partial retraction of the pseudopodia. If the shock is repeated at frequent intervals the effects induced by each stimulus summate, resulting after a minute or two in a true mechanical tetanus, during which there is a concentric contraction of the whole of the protoplasm, which causes the amoeba to assume a globular form. In addition to general mechanical stimulation, the effects of local stimulation have been experimentally studied, by touching or stab- bing the amoeba with a blunt body or with very fine needles. In this case, when a reaction appears, it is at first confined to the point stimulated, whence it is slowly transmitted to the rest of the body. The mechanical excitations of the living matter consist for the most part in a modification of the pressure relations under which it exists. In every case in which there is a difference of pressure at two different parts of the body of any organism, phenomena of excitation are manifested, which, since they are produced by a unilateral pressure, are known as barotactic. Several forms of larotaxis may be distinguished according to the kind of pressure, while it also can be positive or negative, according as the organism turns towards the side of greater or less pressure. Verworn groups under the name of thigmotaxis the tendencies exhibited by many organisms, both animal and vegetable, to adhere to the surface of more solid bodies, or to penetrate through their pores, even in defiance of gravity. Stahl defines as rheotaxis the peculiarity certain organisms exhibit of moving in the direction contrary to a current of water. Since this movement is determined by pressure acting in a particular way, rheotaxis is merely a special form of positive b'arotaxis. Thus far the phenomenon has been studied only in the plasmodia of Myxomycetes and in a few plants ; but it is highly probable that the rise of the spermatozoa in animals and man from the vagina to the uterus, and thence to the oviduct to meet the ovum, is a rheotactic phenomenon, since this movement is accomplished in a direction contrary to that of the current of mucous fluid set up by the cilia of the epithelial cells which line the surface of the uterus, and which vibrate in a direction contrary to the movements of the spermatozoa, Ill LIVING MATTEE A third form of barotaxis is geotaxis, or the well-known property of plants to place themselves with their median axis in a definite direction toward the centre of the earth. The stimulus in this case is afforded by minimal differences of pressure acting on points at different heights of the organism. The stems of trees grow away from the centre of the earth, and are, therefore, negatively geotactic ; the roots grow toward the centre of the earth, and are, therefore, positively geotactic ; further, the leaves, and not seldom the branches, grow in a direction tangential to the earth's surface, and thus exhibit transverse geotaxis. Loeb (1888) discovered that geotaxis is a phenomenon widely diffused among animals also. It is possible to convert animals that exhibit negative, into animals ex- hibiting positive, geotaxis, and vice versa. Many infusoria and 'bacteria exhibit geotactic phenomena. They frequently collect on the surface of the water in which they live (negative geotaxis, Fig. 20) ; at other times they sink down and crowd together at the bottom (positive geotaxis). Knight (1809) showed that geotactic phenomena are determined by differences in pressure acting like gravity on the different points of the vegetable organ- ism. He employed wheels turning in a vertical plane, to which he attached plants in various positions, as well as r , . .. FIG. -20. Glass tube containing Para- germmatmg seeds. He found that all the stems grew in towards the centre of the wheel, while the roots grew away from it. Jensen practically repeated the same experiments on infusoria living at the surface of the water, by rotating the test tubes which contained them in the centrifuge. Provided this were not driven too quickly, so as to make the infusoria, which are specifically heavier bodies, drop to the bottom of the test tube, they remained at the top, where pressure is lowest during rotation. IX. Heat rarely exerts any direct stimulating action on living- matter. In the higher animals, however, the special terminal organs of certain centripetal nerve-fibres are excited by heat. Kiihne was the first to observe thermal tetanus in Amoebae when the temperature was raised to 35 C. On cooling the atmosphere again, the amoeboid movements were slowly restored ; heating to 40-45 C. kills the animal by coagulation of its proto- plasm. When the heat acts on one part only of the amoeba, the moecia. (Jensen.) Inconsequence of negative geotaxis, the infusoria have collected at the top of the tube, although they are specifically heavier than the fluid. 78 PHYSIOLOGY CHAP. stimulus is i'oimd capable not merely of exciting protoplasmic movements, but even of determining their direction up to a certain point. Verworn observed that amoebae always move in a direction opposite to the thermal stimulus, i.e. they exhibit negative thermotaxis. Mendelssohn studied on a ciliated infusorium, Paramoecium, the thermotactic influence of different grades of temperature. When one end of a vessel full of liquid, and swarming with Pararnoecia, is heated to 24-28 C., the creatures move to the cooler end of the vessel ; when, on the contrary, one end of the vessel is cooled below the said degrees, the infusoria move towards the warmer end. Thus there may be positive or negative thermotaxis according to the degree of temperature. In this case, as in cherno- and barotaxis, the movements are determined by the difference of temperature at the two poles of the Paramoecium, differences which can be estimated at about 0-01 C. X. Light rays, like heat rays, act as a direct stimulus on comparatively i'ew elementary organisms. In the higher animals they only affect the nervous elements of the retina, and great intensity is required to stimulate the cutaneous endings of the thermal nerves as well. The skin of invertebrates is also excitable to light. Many observations have been made in order to determine the nature of the action of light upon Protista, and to ascertain whether excitability to light is a general property of protoplasm, or first appears during the phylogenic evolution of living beings. The results with amoebae were purely negative. Other Rhizopoda, however, were seen to contract on sudden illumination. E. Oehl (1886-91) saw that the leucocytes of the blood both of man and frog, when exposed to bright sunshine under the microscope, reacted by active migratory and amoeboid movements, which were not present previous to the photic stimulation. The work of Strasburger and others shows that intensity of light exerts a great influence on bacteria and diatoms, so that up to a certain point of intensity they exhibit positive phototaxis, and approach the source of light ; with greater intensity they move farther off, and exhibit negative phototaxis; at a mid-point they show themselves wholly indifferent. The wave-length of the light rays is also of great importance. Engelmann has shown that the Bacterium photometricum (observed in the micro- spectroscope) swarms into the region of the ultra-red rays, and to a less extent into that of the orange and yellow rays, i.e. towards Frauenhofer's D-line (Fig. 21). The term heliotaxis has long been employed to denote the common property of plants to turn on their axis in the direction of the sun's rays. The phenomenon is particularly conspicuous in plants grown inside the house. Both stems and petioles curve II] LIVING MATTER 79 towards the light that conies in at the windows (positive heliotaxis), while the surfaces of the leaves spread out perpendicularly in the direction of the light rays (transverse heliotaxis). In plants with aerial roots these turn and grow towards the darkest part of the room (negative heliotaxis). !{ I ^ FIG. ll.Lit'-tii-'nini photometricum, in micro-spectroscope. (Engelniann.) The bacteria are collected in the region of the ultra-red and yellow rays. Heliotactic movements are especially favoured by the blue and violet rays ; red and yellow rays are practically inactive (Fig. 22). Loeb (1888) described phenomena of heliotaxis in many animals, which are perfectly comparable with those observed on plants ; they are also determined by the most refrangible rays of the spectrum. The mechanical explanation of the phenomenon is, according to Loeb, that the symmetrical points of an organism Fin. H. Htdiuiii <>j:<'rii1- " This case is realised in growth, where the formation of living substance surpasses its destruction. " If, vice versa, the members of series D grow proportionately to one another, while those of series A remain unchanged, or become smaller, biotonus ^^>1- This condition is the basis of atrophy, and leads finally to death." In a later work (1903) Verworn developed this theory more fully, giving it the name of Biogen hypothesis and enumerating the various indirect arguments, of early or recent date, which tell in its favour, and show how by its application we may arrive at a unitary explanation of the action of the several stimuli upon living matter. "In my opinion" (he concludes) "the principal value of the biogen hypothesis lies in the fact that it enables us to gather up all the vital phenomena under a single, very definite and simple point of view, without contradicting any of the facts hitherto noted. This hypothesis provides us with a clear idea of the phenomena fundamental to the whole of life, and is thus of singular utility in facilitating the interpretation of many complex and controverted problems." " Still " (he adds) " it must once more be pointed out that this is merely a working hypothesis, and that it would be quite fallacious to attribute to it any other value. Whether it be a faithful representation of the real facts, or whether it be in- adequate, matters little ; as a working hypothesis it keeps its value so long as it is useful and fecund in the progress of science. The history of science is richer in fallacies than in truth ; but in the development of the human mind a fertile error is of infinitely greater value than a sterile fact." BIBLIOGRAPHY In addition to the general treatises on anini;il and plant physiology cited above see : PFLUGER. Pfliigers Arch. x. 1875. Cl. BERNARD. Leijons snr les phenomenes de la vie commune anx animaux et aux vegetaux. Paris, 1878-79. E. HERINO. Vorgange d. lebender Materie, " Lotos," ix. 1888. (English transla- tion. Theory of the Functions of Living Matter, by F. A. \Velby. Brain, xx. 1897.) 90 rilYSlnUHJY CHAP.III .1. ROSENTHAL. Lehrbuch d. allg. Physiologic. Leipzig, 1901. S. Lo BIANCO. Mitteihmgen aus d. zoolog. Station xu Neapcl, \vi. 1903. M. VERWOUN. Allgemeine Physiologic. Jena. G. Fischer. 4th rd., 1903. (English translation by Dr. F. S. Lee. Macmillan.) M. VERWORN. Die Biogenhypothese. Jena. Fischer, 1903. J. LOEB. Studies in General Physiology. Chicago, 1905. Recent English Literature : E. AV. TOWLE. A Study in the Heliotropism of Cypridopsis. Anier. Journ. ofPhysiol., 1900, iii. 345. J. LOEB. On lon-proteid Compounds and their rule in the Mechanics of Life Phenomena. Part I. Amer. Journ. ofPhysiol., 1900, iii. 327. R. M. YERKES. Reaction of Entomostraca to Stimulation by Light. 1. Amer. Jonrn. ofPhysiol., 1900, iii. 157. R. M. YERKES. Reaction of Entomostraca to Stimulation by Light. II. Amer. Journ. ofPhysiol., 1901, iv. 405. R. PEARL. Studies on Electrotaxis. I. Amer. Journ. ofPhysiol., 1901, iv. 96. R. PEARL. Studies on the Effects of Electricity on Organisms. II. Amer. Jonrn. ofPhysiol., 1901, v. 301. E. B. HOLT and F. S. LEE. The Theory of Phototactic Response. Amer. Jonrn. ofPhysiol., 1901, iv. 460. H. H. DALE. Galvanotaxis and Chemotaxis of Ciliate Infusoria. Parti. Journ. ofPhysiol., 1900-1, xxvi. 291. \V. M. FLETCHER. The Relation of Oxygen to the Survival Metabolism of Muscle. Journ. ofPhysiol., 1902, xxviii. 474. R. S. LILLIE. On Differences in the Direction of tin: Electrical Convection of certain Free Cells and Nuclei. Amer. Journ. ofPhysiol., 1903, viii. 273. G. P. ADAMS. On the Negative and Positive Phototropism of the Earthworm Allolobophora foctida, as determined by Light of Different Intensities. Amer. Jonrn. ofPhysiol., 1903, ix. 26. A. Moo HE. Some Facts concerning Geotropic Gatherings of Paramoecia. Amer. Jonrn. ofPhysiol., 1903, ix. 238. E. TORELLE. The Response of the Frog to the Light. Amer. Journ. of Physiol., 1903, ix. 466. E. P. LYON. On Rheotropism. I. Rheotropism in Fishes. Amer. Journ. of Physiol., 1904, xii. 149. E. P. LYON. On Rheotropism. Part II. Amer. Journ. of Physiol., 1909, xxiv. 244. G. SMITH. The Effect of Pigment-Migration on the Phototropism of Gamtnnri^ (mnulatus, S. I. Smith. Amer. Journ. ofPhysiol., 1905, xiii. 205. E. P. LYON. On the Theory of Geotropism in Paramoecium. Amer. Journ. of Physiol., 1905, xiv. 421. E. P. LYON. An Outline of a Theory of the Genesis of Protoplasmic Motion and Excitation. Trans. Roy. Soc. of South Australia, 1905, xxix. 7. T. B. ROBERTSON. Investigations on the Reactions of Infusoria to Chemical and Osmotic Stimuli. Journ. of Biolog. Chem., 1905-6, i. 185. 0. P. TERRY. Galvanotropism of J'nfi-o.f. Amer. Journ. of Physiol., 1905-6, xv. 235. J. W. BANCROFT. On the Influence of the Relative Concentration of Calcium Ions on the Reversal of the Polar Effects of the Galvanic Current in Paramoecium. Journ. ofPhysiol., 1906, xxxiv. 444. P. B. HADLEY. The Relation of Optical Stimuli to Rheotaxis in the American Lobster Homarns nmcricanus. Amer. Journ. ofPhysiol., 1906-7, xvii. 326. P. B. HADLEY. Galvanotaxis in Larvae of the American Lobster Hminn-nx ameri can-its. Amer. Journ. ofPhysiol., 1907, xix. 39. J. R. MILLER. Galvanotropismus in the Crayfish. Journ. of Physiol., 1906-7, xxxv. 215. CHAPTER IV THE BLOOD : FORMED CONSTITUENTS SUMMARY. 1. Arrangement of human physiology, and classification of functions. 2. Importance of the blood as centre of the vegetative system and agent of general metabolism. 3. Historical development of haematology. 4. General physico-chemical characters of the blood. 5. Estimation of total quantity. 6. Physical and morphological characters of erythrocytes, and estimation of their relative quantity. 7. Chemical composition. Properties of haemoglobin and its derivatives. 8. Character, composition, and physiological properties of leucocytes. 9. Blood platelets, and elementary granulation of the blood. Bibliography. JUST as no absolute difference can be admitted between the vital activities of plants and animals, so no absolute difference can be recognised between the functions of the individual living cells, tissues, organs, and systems of which the higher organisms, including man, consist. It is nevertheless to be observed that in all complex organisms, whether animals or plants, there is pari 2Jassu with the morphological differentiation of the primitive cell, which occurs during ontogenic development, a functional differ- entiation, resulting in a division of labour, i.e. in the greater or less specialisation of the capacities or functions of the different parts. As in the great industries an ever-increasing development and perfection of industrial products is obtained with the pro- gressive division of the work assigned to the various groups of workmen, so the increasing perfection observed in the scale of living beings is essentially the result of progressive morphological differentiation and functional specialisation in the cells of which the organism is composed (Milne Edwards, 1827). It is evident that the arrangement of the special physiology of man, and the rational classification of his functions, must rest upon this specialisation of the different organs and systems in the higher animals. I. At the commencement of the nineteenth century Xavier Bichat, in his inspired book Sur la vie et la mort, made a sharp distinction between two orders of functions in the higher organisms, which he designated as the functions of organic (or vegetative) life and the functions of animal life respectively. 91 92 PHYSIOLOGY CHAP. By means of the former, says Bicliat in effect, these organisms are constantly transforming into their own substance the materials which they receive from outside, while they continually eliminate the useless products of consumption ; by means of the latter, they feel and perceive the external world, express their sensations, perform voluntary movements under the influence of these, and are able to express their desires and fears, their pains and pleasures. Although modern science has established the unitary con- ception of life, and has refuted the supposed antagonism between the functions of plants and of animals, Bichat's general distinction holds good as the basis of a rational classification. It is a fact that the cardinal function of plants, taken as a whole, is the synthetic building-up of organic matter, while that of animals is its disintegration. On the other hand, it is undeniable that the higher animals possess a system of organs and apparatus which essentially serve the internal life of the body, by preparing and constantly re- newing the pabulum common to all the living elements of which it consists ; while there is a second system which especially serves the external life, by developing the potential energy of the living matter. The first system recalls the predominance of anabolisni in plants, as compared with animals ; the second the predominance of katabolism in animals, as compared with plants. Yet, if w T e attempt to determine exactly which organs and apparatus compose the vegetative system, in distinction to those of which the animal system consists, we encounter difficulties. The embryological criterion, so often invoked in this connection, i.e. the derivation of the different parts from one or other of the three germinal layers, leads to no satisfactory result, since it is now well established that tissues and organs are developed from the external, and yet more from the middle, layer, which obviously belong some to one system and some to the other. Clearly these two systems do not represent two distinct and superposed organisms, but rather two that are intimately connected and interdependent, to be distinguished only by artificial means, contingent to a certain extent on individual judgment and appreciation. It is the obvious function of the vegetative system, as a whole, to keep constant the quantity and quality of the mass of blood, from which is formed the lymph or plasma constituting the common internal medium indispensable to the life of each vital element. This system consists necessarily of the blood, of the cardio- vascular apparatus by means of which it circulates, and of the whole of the glandular organs and apparatus designed for its constant renewal, elaboration, and cleansing. On the other hand, the function of the animal system is to bring the animal through its sense organs into relation with the iv THE BLOOD: FOKMED CONSTITUENTS 93 external world, and to modify these relations in various ways by means of the organs of motion. It consists accordingly of the central and peripheral nervous system, i.e. the sensory and conducting organs, and of the muscular and skeletal system, i.e. the active and passive apparatus of movement. The blood is the centre and objective of all the functions of the vegetative system ; the brain is the central seat and focus of the functions of the animal system. A third order of physiological processes must further be dis- tinguished from the special functions of the vegetative and animal systems, in which both these and, in a certain sense, the entire organism participate. These are the physiological phenomena of general metabolism and the regulation of the balance of output and intake ; thermogenesis and the regulation of the heat balance ; sexual and reproductive functions ; the physiology of the embryo, and of the different stages of uterine life. II. As centre of the vegetative system, the blood contains all the histos;enic substances destined to nourish and renew the o tissues, and all the histolytic products of consumption, useless or noxious residues, to be eliminated. The first, which filter through the living walls of the capillaries, pass in the form of lymph into the interstitial plasma-spaces of the tissues for which they provide aliment ; the second, secreted by the tissue cells, pass into the blood by way of the lymph vessels, and are thence eliminated by the kidneys, lungs, skin, and liver. From the histological standpoint the blood may be regarded as a tissue. It contains a number of formed elements, represented by the corpuscles, and an intercellular substance, the plasma, which is essentially a product elaborated and secreted by all the cells which take part in haematopoiesis and haematolysis. The blood is distinguished from the other tissues by the fact that it is fluid and that it circulates, and is therefore capable of exerting its action on all the fixed tissues, bringing them into relation and binding them together. It thus functions as the centre of the vegetative system, and is the agent of metabolism, i.e. of the material exchanges of the whole body. III. To compress within a few lines the historical development of our physiological knowledge of the blood would be a work of difficulty. In this field there is no one great discovery to be recorded, only the gradual acquisition of separate facts due to the labours of a vast number of observers. We shall confine ourselves to enumerating a few of the principal dates and names as landmarks. The Italian Malpighi (1661) was the first who saw the red corpuscles, while the Dutch Leeuwenhoek (1673) first described them accurately. In England Hewson (1770) also observed the leucocytes, found that many salts delayed or inhibited coagulation, 94 PHYSIOLOCY CII.M-. and foresaw many of the theories that are now generally accepted. A few years later (1704) J. Hunter published an extensive work on the blood, which contained not a few new observations and ingenious experiments. Just as the history of the physics and morphology of the blood begins only in the seventeenth century with the discovery of the microscope, so the history of its chemistry only assumes notable proportions at the commencement of the nineteenth century, after Priestley (1775) and Lavoisier (1784) had laid the first methodical principles of modern chemistry. As the precursors of our present science of haema- tology, we may name Berzelius (1808), Prevost and Durnas(1821), Chevreul (1824), Nasse (1842), Simon (1842), Mulder (1849), Lehrnann (1850) and many others. IV. If we consider the most striking characters of the blood, it is found to be a red fluid (arterial blood, scarlet ; venous blood, dichroic, i.e. dark red in reflected, greenish in refracted, light), somewhat viscous, opaque even in thin layers, faintly salt and sweetish in taste, with a characteristic odour. It is a little heavier than water : the specific gravity of a man's blood varies between 1-057 and 1'066, that of a woman from T053 to 1-061. The reaction of the blood circulating in the vessels is alkaline in the normal state ; extracted from the vessels, it becomes neutral and then slightly acid. It must, however, be noted that in all blood reactions, and, generally speaking, in all the fluids of the body, we have to distinguish between the actual or true reaction and the potential reaction. Recent researches in physical chemistry have brought out the fundamental fact that the degree of acidity or alkalinity of a solution is determined by its content of H + ions and OH - ions respectively. Since the actual reaction of a liquid is that which represents its content of free H + or OH - ions, it is necessary in determining it to make use of means which do not alter the numbers of these ions. The potential reaction is that which represents the degree of acidity or alkalinity of a liquid when the electrolytes which it contains are all fully dissociated into their ions. The determination of these two kinds of reaction leads in the case of the blood to very different results. While according to the potential reaction the alkalinity of the blood corresponds to a soda solution of 0'2 - - 4 per cent, according to the actual 1 3 or true reaction it would be that of - ]0 OQO OQ() N of soda, which is practically neutral (Farkas). The Pycnonii ti'ir M>-f1n>,l is certainly the m carried on can IK- recorded (Fig. 24). After carefully cleaning and drying the pycnometer, it is weighed, tirst empty, then when filled with distilled water* It is then washed out with alcohol and ether, dried again, and weighed once more when rilled with the Mood to lie examined. The weighing must lie accurate to ^ ingrni. The weight of distilled water at lf> ( '. lieing equal to 1, it is easy to calculate that of blood at the same temperature. The areometric methe indirect methods rather determine the specific gravity of the corpuscles than that of the Mood iii Me into contact with the blood to be examined, they are washed rapidly with a tine spray of distilled water. The Titration Methods, which consist in determining the quantity of an acid or alkaline solution of a given strength to lie added to the liquid under examination, in order to modify the colour of an indicator, merely give the potential, and not the actual, reaction of the fiuid. Apart from errors due to the nature of the indicator, it must be remembered that not only the quantity 96 PHYSIOLOGY CHAI-. of tree 11 + and OH- ions remaining in the fluid, but, further, the quantity of H+ and OH- set live in consequence of the modifications of chemical equilibrium between non-dissociated and associated molecules, are determined. The titration methods most commonly employed to estimate the alkalinitv of the blood are as follows : 1. Zuntz neutralised the alkalinity of the blood by a titrated solution of phosphoric acid, 1 c.c. of which corresponds to 0'005 grm. of sodium carbonate. Litmus-paper is used as the indicator. Lassar, on the other hand, employs a decinormal solution of tartaric acid (7'5 grins, of acid per litre). 2. Landois adopts the decinormal solution of tartaric acid, and a perfectly neutral, saturated solution of sodium sulphate. As indicator he uses the finest litmus-paper. With these two solutions ten mixtures are made in tin- following proportions : N I. 10 parts n tartaric acid to 100 parts saturated sol. XaS0 4 . II. 20 90 X. 100 10 The first mixture is then aspirated to a distance of 8 mm. along a. graduated pipette made of a glass tube 1 mm. in diameter, and the blood to a distance of 16 mm., i.e. 8 mm. of each fluid. This mixture is emptied into a watch-glass and the reaction tested. Each successive mixture is employed in the same way until the alkaline solution becomes acid. The degree of alkalinity corresponding to the several mixtures is as follows : I. =0-036 per cent NaOH. VI. = 0-216 per cent NaOH. 11=0-072 VII. = 0-252 III. = 0-108 VIII. = 0-288 IV. = 0-144 IX. = 0-324 V. = 0-180 X. = 0-360 Jaksch has modified Landois' method in practice as follows. He too employs a solution of y^ tartaric acid and a concentrated solution of sodium sulphate. He dilutes the first solution 10 and 100 times, making solutions of 1C "N and - - tartaric acid respectively. These solutions are mixed with the solution of sodium sulphate in eighteen mixtures, which contain : N 1. 0-9 c.c. . Q acid with O'l c.c, of NaSO 4 . II. 0-8 0-2 IX. 0-1 0-9 X. 0-9 c.c, -jjj- 0-1 XL 0-8 0-2 O'l c.c. of blood is dropped into each watch-glass, stirred up, and the reaction tested with litmus-paper. The solutions correspond to the following degree of alkalinity of the blood : I. 0-360 NaOH in 100 grms. of blood. II. 0-320 III. 0-250 IX. 0-040 X. 0-036 XVIII. 0-004 The actual reaction of the blood is measured by the Electrometric Method (concentration cell). Particulars will be found in any modern text-book of physics. [v THE BLOOD: FORMED CONSTITUENTS 97 The blood has the highly important property of coagulating spontaneously. In a few moments (3-12 minutes for human blood) after it has been taken from the blood-vessels it is trans- formed into a gelatinous mass, which assumes the shape of the vessel that receives it. It is the formation of this clot which checks the continuation of haemorrhage in small injured vessels which would otherwise lead to the death of the animal. Clotting depends on the formation and separation of a protein from the plasma, i.e. fibrin (which, as we shall see, does not pre-exist as such) in the form of a fibrillar reticulum of such excessive fineness, that it encloses in its meshes not merely the whole of the corpuscles, but also the entire liquid portion of the blood. This fact appears the more marvellous when we consider that the amount of fibrin formed during coagulation never exceeds 1 per cent of the mass of blood, but is more often represented by a fraction, 04 per cent, of this, and may even fall to the minimum of O'l per cent. The separation of the fibrin from the mass of blood can be eiiected by prolonged washing of the clot (Malpighi, 1666), or by whipping the freshly-extracted blood (Ruysch, 1707). In this last case the fibrin clings to the rod used for whipping as a fibrous, elastic, whitish mass ; and blood thus defibrinated is incapable of clotting. From the clot containing the whole mass of blood a yellowish fluid gradually separates out in consequence of the physical retraction of the fibrous reticulum, the so-called serum, which represents that part of the plasma that remains liquid after coagulation. When all or nearly all this serum has separated out from the clot, the latter is seen to be considerably diminished in volume, though it still keeps the form of the vessel. The clot thus reduced by the separation of the plasma is sometimes termed the crassamentum . In blood which has been rendered incoagulable by defibrina- tion, the red corpuscles, being heavier than the serum, tend to fall to the bottom of the vessel, so that an almost transparent upper layer is formed by degrees, consisting principally of serum, with an opaque lower layer formed almost exclusively of the mass of corpuscles. The separation of the serum from the corpuscles is effected with maximal speed and perfection by the Centrifuge, which can lie. performed with the elegant little model represented in Fig. 25. If coagulation is delayed in blood newly drawn from the veins (as is often observed in human blood during inflammatory diseases, and normally in horses' blood) there is again a partial separation of the plasma from the red corpuscles, and the clot subsequently formed presents a greyish superficial layer of greater or less density, known as the buffy coat, or crusta pklogistica, which consists of coagulated plasma mixed with leucocytes, without any red corpuscles. VOL. I H 98 PHYSIOLOGY CHAP. V. The estimation of the total quantity of the blood, or its relations with the weight of the animal, presents great practical difficulties. The older anatomists held very exaggerated views on the quantity of blood in man, estimating it erroneously by the amount of injection mass that can be forced into the blood-vessels of a dead body. Far too low values, on the other hand, were obtained at a later period by the method of completely bleeding the animal (Herbst, 1822), since this does not sufficiently take into account the quantity of blood left in the vessels, which may vary considerably in different cases. PIG. 25. Hedin's small centrifuge. By means of three cogged wheels enclosed within 1 -1, 3, each turn of the handle is multiplied 100 times from the axis A, the apex of which carries a cross- piece, with the test-tube holders jip, which are kept horizontal during the rotation. A better method is that carried out by Lehmanu and Ed. Weber on two criminals (1853). They weighed the individuals before and after decapitation, and from the difference in weight estimated the mass of blood lost by bleeding. They took a sample of this blood. They then injected water through the arteries of the trunk and head, until it flowed almost colourless from the veins, and lastly determined the weight of the solids contained in the Wood and in the washings. From these determinations they calculated the quantity of blood left in the body after decapitation. It is obvious that this method must give too high a result. The introduction of water into the vessels must extract not only iv THE BLOOD: FOEMED CONSTITUENTS 99 the fixed constituents of the blood remaining in the system, but also such as have penetrated by the lymphatic system and by diffusion from the tissues, during and soon after the bleeding. In one of the criminals, who weighed 6.0,540 grrns., the mass of the blood weighed 7520 grins., i.e. one-eighth of the body- weight. More exact results were obtained with the chromometric method, which is based on the colouring properties of the blood pigment (haemoglobin). It was first employed by Welcker (1854) and was perfected later by Gscheidlen (1873). A little normal blood is first drawn from the animal and weighed ; the whole of the blood that can be extracted by bleeding is then collected ; that left behind is subsequently washed out of the system, by irrigating with a stream of isotonic (0'60-0'55 per cent) salt solution ; then, after removing the contents of the gastro-intestinal canal, gall bladder and urinary bladder, the viscera are minced up and soaked for several hours in the saline fluid used for washing ; lastly, the washings are mixed with the mass of blood obtained by bleeding. The blood-content is calculated from the coloured liquid obtained, after determining the quantity of saline that must be added to the weighed specimen of blood in order to obtain the same degree of colour. To make the experiment more exact it is advisable to saturate the haemoglobin with carbon monoxide, in order to secure the same degree of colour in both mixtures. The calculation for determining the quantity of blood contained in the body is very simple : If a is the quantity of blood extracted in the first bleeding, ;/: the quantity of blood left in the body, b the quantity of physio- logical saline employed to wash out the vascular system and organs of the animal, c the quantity of physiological saline necessary to make the colour of the blood a equal to that of' the blood x, plus the fluid b (a quantity which is known to us, and which we may, to simplify matters, denote as . man; li, pigeon; 7, tench; 8, lizard; !, f'ro.u ; 10, jiroteus. in which they are elliptical) ; nucleated and elliptical in birds, reptiles, amphibia and fishes (Fig. 26). The red corpuscles of man have a diameter of 7-8 //. and a depth of 1'7/t; in other mammalian animals they are even smaller ; in birds and the lower vertebrates they are much bigger (21 ^ in frog, 29 /j. in Triton, 58 //, in Proteus). Viewed from above, and isolated, they are greenish-yellow in colour ; seen from the side as a rouleau of discs, they are red (Fig. 27) ; to them the blood owes its char- acteristic colour, and they render it opaque. They are soft, almost gelatinous in consistency hence they easily change their shape ; but they are perfectly elastic, and recover their original form directly the contracting force ceases to act on them. Eed corpuscles may be divided, according to their affinity for staining, into orthochromatic and polychromatic (Ehrlich). The orthochromatic are the most numerous, and stain with aurantia and eosin. The polychromatic, which are much less frequent, take up fuchsin when they are stained with tri-acid ; with eosin- methylene-blue they stain violet, etc. lied corpuscles are classified IV THE BLOOD: FORMED CONSTITUENTS 101 according to their form and size (distinctions which concern the pathologist) into normal erythrocytes, micro- and inacrocytes, and poikilocytes (pear-shaped, rod -shaped, etc.). Again there are red corpuscles which exhibit granules of different sixes and shapes in their protoplasm, and which will stain with all the basic dyes (basophile granulation). On changing the stains, the rigures produced assume quite different forms : this shows that the figures that we see do not correspond exactly with the pre- existing arrangement of the chromatic substance, but depend on the different physico-chemical actions exercised by each individual colouring substance (Cesaris Demel). The significance of these granules is uncertain ; by some they are considered to be the remains of nuclei, according to others they are protoplasmic formations. ~\ ' > ...... ' f , FIG. 27. Red blood -corpuscles of man. (Magnification, 6^0 diameters.), .Some are seen flat, others in profile, the majority are disposed in rouleaux. Although Schultze has described active movements of the protoplasm in the nucleated erythrocytes of the chick, it is very doubtful whether the red corpuscles of mammalia are capable of expanding and contracting in the medium in which they normally live. When, however, they are taken out of the vessels, and cooled or warmed, or excited by induction shocks ; when the degree of concentration of the plasma in which they float is altered by the addition of water or of saline solutions ; when they are brought in contact with extraneous chemicals, they readily change their shape, assuming a mulberry-like or even prickly (crenate) appearance, and extending or retracting different segments of their protoplasm, as if undergoing amoeboid movements. The former changes are the effect of altered osmotic conditions, the latter are probably to be regarded as active movements (Figs. 28 and 29). The capacity of erythrocytes for active movements in certain special abnormal conditions is confirmed by the observations of A. Cavazzani. He noticed that when blood was collected in an isotonic or hypotonic solution of sodium chloride, to which potassium 102 PHYSIOLOGY CUM-. ferrocyanide or a highly dilute solution of potassium sulpho- cyanide had been added in the proportion of about 1 per 1000, and then examined under the microscope at a temperature of .">r>-37 0., the erythrocytes of man and other mammalia (not of birds and batracians) put out delicate prolongations like cilia, the rapid vibratory movements of which enable the corpuscles to oscillate, rotate, or move forward. These cilia-like pseudopodia FIG. 28. Successive effects upon erythrocytes of discharge from a Leyden jar. (Rollett.) a, normal erythvoeyte ; '/, rosette form; <, mulberry form; tnev CUe ano - b, action of a solution of salt ; break up when reintroduced into the e, action of tannic acid. . i . T f> c -\ i circulation. It transfused into animals of a different kind they do not survive, but degenerate and disin- tegrate more or less rapidly, owing to the heterogeneous plasma with which they are brought in contact. The direct enumeration of the corpuscles contained in a given quantity of blood (1 c.nim.) was correctly performed for the first time by Vierordt and Welcker (1854), the results they obtained having been confirmed by more recent observers. The method and apparatus have been perfected, and are now practical and easily applicable for clinical purposes. We must here confine ourselves to naming those of Malassez, Hay em, and Thoma-Zeiss. Haemacytometer of Thoma-Zeiss. In order to count blood-corpuscles with the Thoma-Zeiss apparatus, the point of the capillary glass pipette (Fig. 30, I) is dipped into the drop of blood to be examined, which is obtained by IV THE BLOOD: FORMED CONSTITUENTS 103 pricking the finger with a needle. A column of blood is aspirated by means of the rubber tube to division 0'5 or 1 of the pipette, and after quickly drying the lower end, the bulb of the pipette is tilled Tip to the figure 101 (which expresses its capacity in c.mm.) with 3 per cent salt solution, or with Pacini's fluid as modified by Hayem and Gram (corrosive sublimate 0-5 grin., sodium sulphate 5 grins., sodium chloride 2 guns., distilled water 200 grins.). It is then sufficient to shake the pipette for a few moments in order that the glass ball (), which is loose inside the bulb, may mix the blood with the salt solution, and make the fluid homogeneous. As the division 0'5 corresponds exactly to -o-J-o of the total capacity of the bulb, and the figure 1 exactly to ,^ 7 , we know that the mixture obtained is in the ratio of 1:200 or 1:100. The counting is done upon a carrier (II) with a groove (6), the bottom of which is divided by lines cut with a diamond into 400 minute, squares (as is shown in III). Into this groove, the capacity of which is O'l c.mni., a drop of the blood solution contained in the bulb of the pipette is intro- duced, care being taken to drive out the liquid contained in the capillary portion, which has not been mixed with the blood, When the drop is placed in the groove, a cover glass (.) is quickly applied, and after letting the preparation rest for a few minutes upon a perfectly horizontal surface, in order that the red corpuscles may be spread evenly upon the floor of the groove, the counting is undertaken under a magnification of 200 II of thirk glass _. *. f t' a y -V-.1 ni FIG. 30. Thoina-Zeiss Haemacytometer. I, Graduated pipette (Potain's mixer) ; II, cell for counting corpuscles, side view ; III, squared divisions of bottom of haeimicytometer. diameters. The number of the corpuscles counted is divided by the number of squares examined, which should never be less than 200 ; thus obtaining the average of the red corpuscles contained in each square, which represents T - L nr c.mm. Hence, if we wish to know the number of corpuscles in c.mm. it is only ne<-earv to multiply the number found first by 4000, and then by 100 or 200, according as the blood has been diluted lOO or 200 times. To take a practical example : If 1225 corpuscles are counted in 250 squares, VOL. I H I 104 PHYSIOLOGY CHAP. :iinl Ihr Mood has been diluted 200 limes, 1 e.mm. of blood will contain < 4000x200 = 3,920,000 red corpuscles. The while Mood-corpuscles can lie counted at the same time; but il' a separate enumeration is desired lor the sake of accuracy, the blood must be agitated with a - 3 per cent solution of acetic acid, in which the red corpuscles will dissolve while the white remain intact. Biedin's Haematocrit is an apparatus for determining the total volume of red corpuscles in 100 parts of blood. It consists of a small centrifuge (Fig. 25, p. 98) and of two graduated tubes (a, ', Fig. 31). The determination is carried out as follows : A small quantity of Miiller's fluid (sodium sulphate 1 grm., bichromate of potash 2 grins., distilled water 100 grins.) is taken up with a pipette, and dropped into a small porcelain dish. The finger is then pricked with a lancet so as to obtain a large drop of blood. With the same pipette a quantity of blood equal to the quantity of M tiller's fluid is taken up, and emptied into the same dish. The two Huids are then thoroughly mixed with a glass rod, with the double object of retarding the coagulation of the blood (the mixture will not clot under half an hour) and of fixing the red corpuscles in their natural size. The graduated tube is then filled with the mixture thus obtained, by taking up the fluid from the dish directly into the tube, KK:. : per cent (Hoppe- Seyler). The dry substance of the erythrocytes consists principally of haemoglobin (87-95 per cent), so that the strorna is a very small amount (13'5 per cent). For the total quantity of the blood, about 13 - 8 per cent haemoglobin lias been calculated for man, and about 12'6 per cent for woman. Hoppe - Seyler was the first to investigate the chemical properties of haemoglobin (18GG-71) and to recognise that although it is a colloid body, it is capable of crystallising in different forms in different animals, all, however, belong- ing to the rhombic system (with the exception of squirrel's blood, which crys- tallises in hexagonal plates ; Fig. 32). To obtain crystals of pure haemoglobin, they must first be dissolved in the blood by freezing and gradual melting ; the blood in a layer 2 mm. deep is then allowed to evaporate slowly in a flat, wide-bottomed capsule. The different forms Of Fl<: - 32. -Haemoglobin crystals. (Fuuke ) a, From 7iian ; o, guinea-pig ; c, squirrel. oxyhaernoglobin crystals, the different quantities of water of crystallisation which they contain, their different solubilities and different resistance to decomposing agents, in short the varying results of elementary analysis, all point to the conclusion that oxyhaenioglobin is not identical in different animals. It is a highly complex, iron-containing protein, the formula of which was determined by Hiifner from analysis of the haemoglobin of dogs' blood. Each molecule of haemoglobin combines with a molecule of oxygen to form oxy haemoglobin. Haemoglobin has a greater affinity for carbonic oxide than for oxygen, and forms with it carl}oxy haemoglobin, which, unlike oxyhaemoglobin, does not reduce with deoxidising agents. While carbonic oxide turns out oxygen, the latter has difficulty in driving carbonic oxide out of its combination with haemoglobin. To this fact is due (in part, if not wholly) the toxic action of carbon monoxide. With a series of oxidising agents, particularly with nitrites, n 10S riLYSIOLOCY CHAT. FIG. 33. Haemhi crystals. (I'reyer.) permanganate of potash, potassium ferricyanide, active oxygen, hydrogen peroxide, etc., haemoglobin is converted into methaemo- i/fnh/n, which is an isomrr of oxyhaemoglobin, but in which the <>xygrn is more closely comhined, so that it cannot he driven out by the unaided vacuum. Methaemoglobin can also be formed in circulating blood by the excessive use of chlorate of potash and other substances used in medicine in recent years as antipyretics. Haemoglobin undergoes spon- taneous decomposition slowly under the influence of air and water, rapidly as the effect of acids or alkalies, or of heating. Another iron-containing pigment is thus formed, haemocfiromogen, which oxidises readily in the presence of oxygen and is con- verted into haematin, which gives a brownish colour to the solution. Along with haeniochrornogen and haematin, the decomposition of haemoglobin gives rise to con- siderable quantities of acid or alkali albumin, according as acids or alkalies are used to break up the blood pigment. From these facts Hoppe-Seyler regards haemoglobin as a protein, which con- sists of an albumin, associated with an iron-containing pigment, haeinochrornogen. One hundred parts of haemoglobin contain ninety-six parts albumin and four parts pigment. Haemin must be noted among the decomposi- tion products of blood pigment on account of its great practical im- portance ; it crystallises in the form of small rhombic plates or rods, of a shining brown colour (Fig. 33). Haemin crystals are of great importance in forensic medicine, in the detection of blood-stains. A trace of dried blood suffices to obtain them. A grain of sodium chloride is added, dissolved in a few drops of glacial acetic acid, and cautiously heated over a spirit lamp until gas bubbles are formed. Haemin is haematin hydrochloride, and to obtain pure haematiu it is necessary to start from this combination. It is a sulphur-free compound, but is richer in iron than haemoglobin. When treated FIG. 34. Haematoidin crystals. (V. Frey.) iv THE BLOOD: FORMED CONSTITUENTS 109 with sulphuric acid, the haematin loses its iron and takes up water, turning into haematoporphyrin, an iron -free pigment somewhat resembling haemoglobin in colour. Another iron -free derivative of haemoglobin, which forms spontaneously in a crystalline form in the corpora hi tea and in old haeinorrhagic foci, is haematoidin (Virchow), now regarded by chemists as identical with bilirubin, one of the principal bile- pigments (Fig. 34). It seems clear that all the colouring matters of bile and urine are derived from successive transformations of blood pigment; but with the exception of bilirubin, which forms spontaneously, only one of the urinary pigments, urobilin, has at present been produced artificially from haemoglobin or haeuiatiu. Many of the pigment substances above recorded, haemoglobin, oxyhaemoglobin, carboxyhaenioglobin, methaemoglobin, haemochro- mogen, haematin, haematoporphyrin, urobilin, possess the important property, when examined in layers of known thickness and con- centration, of absorbing well-determined and distinct zones of the spectrum in aqueous solutions, acid or alkaline, as shown in Fig. 35. It is important to note that while haemoglobin shows a single absorption band between the Fraimhofer D- and E - lines, oxyhaemoglobin and carboxyhaenioglobin show two bands that almost coincide in the two cases, lying practically within the same region of the spectrum. Apart from the different tint exhibited by oxy- and carboxyhaenioglobin, the former being the pinker, they can, however, readily be distinguished by adding a reducing substance, e.g. carbon disulphide, to the two solutions, when the spectrum of oxyhaemoglobin is speedily transformed into that of haemoglobin, while the spectrum of carboxyhaenio- globin undergoes no modification. To determine the relative quantity of haemoglobin contained in a given quantity of blood, several instruments have been adopted. The simplest and most convenient Haemoglobinometer is Gowers' apparatus, provided with a standard solution of CO-haernoglobin. The method, as accurately described by Haldane, 1 gives extremely good results. For more accurate quantitative determination, either of the haemoglobin or of the pigments derived from it, the Spectro-Photometric Method must lie employed. This method is based on the law that the coefficient of extinction of any coloured solution is (for any given zone of the spectrum) directly proportional in its concentration, i.e. C : E = C' : E', when C and C' indicate the correspond- ing coefficient of extinction By coefficient of extinction of a fluid is meant the negative logarithm of that intensity of light which remains after it has traversed a liquid stratum of the depth of 1 c.c. (Kriiss, Kolorimetrie n. quantit. Spectralanalyse, 1891). From the above equation it follows that -n--:^-; this ratio, known as that of absorption, is a constant for the same colouring substance. Xow, if 1 Junr/1. of Ptiysiol. xxvi. 497. no PHYSIOLOGY CHAP B D E b 6 9 10 Fio. 35. Absorption-spectrum of blood-pigment ami its derivatives. 1, Oxyhaenio^lobin ; 'J, haemoglobin ; ::. methaemoglobin and haeinatin in acid solution ; 4, liaeinatin in alkaline solntiun ; ">, haematoporphyrin in acid solution; 6, haematoporphyrin in alkaline solution ; 7, haemochromogen in alkaline solution ; s, earbpxyhaemoglobin and carboxyhaemochromogen ; y. sulplio-methaemoglobin ; 10, hydroliiliruliin and urobilin in acid solution. IV THE BLOOD: FORMED CONSTITUENTS 111 the absorption ratio be represented by A, the coefficient of extinction by E, and the content of colouring matter in 1 c.c. (calculated in grams) by C, it follows tliat C will be equal to A x E. The most exact of the various instruments constructed for the determination of coefficients of extinction is that of Kruss. This i'as shown by Fig. 36) resembles an ordinary spectroscope and differ.- from the. spectro-photometers of Vierorclt, Hiifner and others, in that the two slits//' (Fig. 38) which give the two spectra, one above the other, enlarge and contract in both directions with a single movement of the screws V and V. To use this apparatus, fill a small pipette of capillary bore with blood to a Kn;. :;. Spectro-photometer of Kruss viewed as a whole. The extreme end of the eye-piece is shown in Fig. 37. The extreme end of the objective is shown in detail in Fig. 38. The lettering corresponds. The absorption-chamber containing the solution of the pigment, to be I'xaiainod is shown in Fig. 3!>. The third branch s. illuminated by a gas flame, projects the millimetre scale on to the spectrum. given capacity, say 20 c.mm. This blood must lie rapidly expelled into a small beaker in which a measured quantity of distilled water has first been placed, so that the blood is diluted in known measure. The degree of dilution varie> with the greater or less colouring power of the blood to be tested, but as a rule the ratio of 1-200 is preferred. The pipette which held the blood should be washed out several times with the water used for dilution, and the liquid must be agitated till it is homogeneous in colour. The absorption chamber (Fig. 39), which is a crystal cell with parallel faces, is then filled, and a cube of glass, D, of the exact diameter of 1 cm., introduced, to which the name, of Sehultz' cube is given. The two absorption spectra are those of two strata of the same fluid differing by 1 cm. in depth. The extinction coefficients for human oxyhaemoglobin have been deter- mined in two different regions of the spectrum, i.<:. D 32 E - D 54 E and D 63 E - D 24 E : 112 PHYSIOLOGY CHAP. in which Hiifuer has determined the absorption ratios or constants for, viz. : 0,001330 and 0,001000 respectively. The limits of these spectral positions, which are comprised between the Fraunhofer D- and K- lines, may be expressed in wave -lengths by means w o / / \ v : IS j n I 4 J D ! 1 1 1 - . I/!,.. :ir. tt'. Micrometer screw, iliviiled into hundredtlis, each turn of which displaces the index of the scale S by one division. This serves to regulate and measure the width of the slit/, which can be carried by a horizontal movement to the centre of the eye-piece. /,-, Micrometer screw divided into hundredtlis. each turn of which displaces the index of a scale n by one division. This moves the eye-piece by an angular development to carry it to any given region of the spectrum. of the table published by Kriiss (as above cited). In practice they can be obtained by finding on the illuminated scale of the spectrum (Fig. 36, s) the values corresponding to the two wave-lengths calculated, and limiting tlie spectral region which these comprise by the horizontal screw of the telescope (Fig. 37), and that marked W, which controls the slit / of the eye-piece. The ab- sorption chamber A is then placed on its support between the plane of the spectrum and the source of light, taking care that the upper surface of the cube D corresponds exactly with the line of division between the first and second slit, and that the aperture of these corresponds to a complete turn of the screw : a turn divided into 100 parts, as shown on the scale affixed to the screws v and v' in Fia 38. e e e e 1 I " ^ ~~ JB, o s N /. f 1,.. "" '". . c> 1 ''" L . - f. hv-V-p jajr y -Jfc / ':-. ' 'v,. ., I ! -'' i" u - ? V? r - e e e Oi i then looking through the Fn;. .-.8. I', f, Micrometer screw divided into instrument, two positions of the hundredths. serves to widen or narrow the slit /./', 'ii i -ui i i by simultaneous displacement of the two plates spectrum Will be Visible, one below that confine it. the other : one is brighter, corre- sponding to the cube of Schultz, the other obscured by the absorption due to the solution of oxyhaemoglobin. The slit corresponding to the blighter part of the spectrum is then narrowed until it assumes the same tone of light as the other, and the scale on the screw read to show how many turns were required to produce uniform obscurity. From this number, which indicates the intensity of the [V THE BLOOD: FOKMED CONSTITUENTS 113 light remaining after the luminous rays have traversed the colouring matter of the blood, the negative logarithm that represents the extinction co-efficient can be calculated, and this must be multiplied first by the constant of the spectral tone obtained, and then by the degree of dilution of tin- blood. Thus it is calculated how many grams of haemoglobin art- contained in 1 c.c. of blood. Practical Example. Let the blood under examination have been diluted 200 times, and the first spectral region be that in which the constant is 0'001330, the intensity of the remaining light will be found to be 0'255 ; to calculate the amount of oxy- haernoglobin contained in 1 c.c. of the blood, multiply 0'001330 by 200, and then by the negative logarithm of 0'255, i.e. bv 0'5935. O t/ In this case the oxyhaemoglobin of 1 c.c. of blood will be equal to G'1578 grin. VIII. The White Blood 3 Or LeUCOCyteS are FIG. W.A, Absorption-chamber with parallel faces; r<-vi->i-i->l/ifn <->nllc. D, Schultz' cube, made of glass 1 c.c. in depth, in- and complete cells, con- tl ; )(iuce ,i into the chamber." sisting of naked granular protoplasm, with one or more nuclei, which are not easy to dis- d FIG. 40. Different kinds of human leucocytes examined either in the fresh state, or after fixation with vmiuiis reagents, magnification about 1000 diameters (partly from Kauthack and Hardy), a, a', li, Fresh leucocytes of three different sizes, in the resting state ; <:., the same in amoeboid state ; . Erythrocytes and 111 j-i 1. ' i j j? platelets in small mesenteric vein improbable that they are derived from of mouse. (Osier.) the latter, owing to disintegration of cellular protoplasm. Besides blood-platelets, the older observers detected granules and irregular protoplasmic fragments of various dimensions (and quite distinct from the fat drops that dissolve in ether) in the blood, which evidently originate in the disintegra- tion of the protoplasm of the lymphatic cells or leucocytes; on this they founded the hypothesis that the platelets too are derived from the disintegration of leucocytes. In accordance with this theory, Fano has demonstrated that there are scarcely any platelets in dog's lymph. Probably this is due to the fact that the younger lymphatic cells predominate in lymph, and that their protoplasm disintegrates less readily. It should also lie added that blood-platelets of characteristic form iv THE BLOOD: FOEMED CONSTITUENTS 119 do not exist in blood that has been whipped and defibrinated, and that they disappear from the blood of dogs that have been repeatedly bled, with subsequent infusions of the same blood after it has been defibrinated. In such animals nothing otherwise abnormal can be detected, and the blood -platelets gradually reappear, and are present in their usual number after a few days (Gad). On the theory that the platelets originate in the decomposition of leucocytes, the explanation of these facts may be that the young leucocytes, supplied to the blood by the lymphatic system, require a certain time to develop, become adult, grow old, and disintegrate, when their nuclei give rise to the formation of new platelets. On the other hand, not a few of the recent workers in this field incline from many standpoints to the view that the platelets originate from the red corpuscles. Koppe, Hirschfeld, and Pappenheim observed that a certain number of erythrocytes are spherical in form, without depressions, within which are masses that stain pink with tri-acid, and faint turquoise with methylene blue, and which when isolated differ in no respect from blood - platelets ; while blood -platelets can often be distinguished among the erythrocytes. Other observers hold that the erythrocyte consists of two parts a central, and a peri- pheral stratum. The peripheral layer contains the haemoglobin (Foa) : beneath this lies the true protoplasm. It must also be remembered that according to Engel, every non- nucleated blood -corpuscle has at one time or other been one of those nucleated corpuscles of which the mantle contains haemoglobin and is aurantiophile, its chroniatin consisting of nuclein, and its achromatic acidophile substance containing protein. When, under normal conditions, the nuclei of the red nucleated corpuscles apparently disappear in kariolysis, the nuclei lose their shape, but the chemical substances of which they are composed persist under other forms. One form of these nuclear rests is the basophile granulation of the erythrocytes (see below) ; the other, more common, form is represented by the almost amorphous blood platelets. On this theory it may be said that every red corpuscle of the depressed form has already lost its platelets, wiiile erythrocytes from which the platelets are on the point of issuing, or in which they are still confined within the corpuscle, are the more nearly spherical. This mode of origin of the blood-platelets would account for the appearance they sometimes present of escaping, even where detachment is not complete. The body thus detached may, even if rarely, resemble a nucleus surrounded by protoplasm. Foa has recently (on repeating with modern methods of fixing and staining the experiments he made in 1889, in collaboration with Carbone) confirmed the existence of platelets in the spleen VOL. i i c 120 PHYSIOLOGY CHAI-. which are identical with those circulating in the blood ; these, he maintains, are not simply deposited there, but originate in situ. According to Poa the platelets are autonomous elements, and since they are composed of protoplasm and nuclear substance, are real cells sui generis, capable of multiplying by direct division in the circulating blood. In view of the importance assigned to the platelets in respect of blood coagulation, we shall return to them after considering the chemical constitution of blood plasma. The microscopic examination of the blood can be made with fresh or fixed preparations. It is essential to use slides and cover-glasses that have been scrupulously cleaned (first in alcohol containing HC1, and then in ordinary alcohol) and well dried with a linen cloth. The blood required is obtained by pricking the ball of the finger or lobe of the ear with a needle (better, a lancet), so that the blood wells out in drops without employing compression. In order to examine fresh preparations microscopically, it is only necessary to take up a drop of blood on the cover-glass and lay this on the slide with the drop downwards. If the glasses are clean, the blood spreads uniformly between them, and the preparation only needs a gentle tap on the cover-glass to distribute the morphological elements in an even layer and make it ready for observation. In order to keep the formed constituents of the blood alive for prolonged observation, a drop of blood must be gently compressed between two cover- glasses, which are then separated by drawing one across the other. One of these films is laid over the central depression of a special slide, such as is used for the observation of bacteria in hanging drops. The margin of this de- pression is previously filled with vaseline to prevent the intrusion of air, which would cause the preparation to dry up making a minute moist chamber. The preparation is then placed on Schultze's warm carrier and kept at the required temperature. The fixing of the blood for microscopic study is performed in two different ways, by the wet or the dry method. To fix it by the wet method the blood is collected iii a watch-glass and the various fixing solutions added. Such are solutions of osmic acid, corrosive sublimate, palladium chloride, Kleinenberg's picro-sulphuric acid, Flemming's osmic -chrom- ace tic mixture, etc. When completely fixed, the solution is removed, and the preparation can be examined immediately or after staining. Fixing by the dry method is effected by warming the film preparation. It must be dried in the air, and then passed 6-10 times through the flame of a spirit lamp, care being taken not to scorch it ; or it may be laid for about an hour on a copper plate, warmed to 120. Fixation is also effected by placing the air-dried blood film for an hour in a mixture of equal parts of absolute alcohol and ether. Excellent results are obtained by warming, and then dipping into alcohol and ether. Staining is necessary in studying the detailed structure of the formed elements of the blood. To stain fresh preparations, weak solutions of iodine, methyl-violet, niethylene-blue, eosiu, etc., must be used. For staining dry preparations, countless methods are described in special text-books, but we must here confine ourselves to the most ordinary, which are also the most practical for the doctor. The film-preparations are passed 6-10 times through the flame of a lamp, and then placed for about half-an-hour in equal parts of absolute alcohol and ether. They are then dried again in the air, and stained in a watch-glass with Ehrlich's acid haematoxylin (haematoxylin 2 grms., absolute alcohol 60 grms.). To this first solution is added the following mixture, which has previously been saturated with alum : glycerin 60 grms., distilled iv THE BLOOD: FORMED CONSTITUENTS 121 water 60 grins., acetic acid 3 grnis. In 5-10 minutes the cover-glasses are taken out of the haematoxylin, washed in water, and stained for the second time by dipping them for a few moments into a 1 per cent solution of eosin. They are then washed again in distilled water, wiped at the edges with filter-paper, dried over the i flame, and mounted on the slide with a drop of Canada balsam dissolved in xylol. The nuclei and blood-platelets stain blue with the haematoxylin, the protoplasm pink with the eosin. A copious literature has recently sprung up in regard to osmotic phenomena, and the resistance of the erythrocytes to yielding their haemoglobin, when brought into salt solutions of different concentrations. Since, however, this subject is intimately connected with the physico-chemical structure of the blood plasma, we shall consider it in the next chapter. The important question of the origin, formation, and destruction of Erythrocytes and Leucocytes will be discussed in treating of the function of the haematopoietic and haematolytic organs. BIBLIOGRAPHY WELCKER. Zeitschr. f. rat. Med., 1858. PREYER. Die Blutkrystalle. Jena, 1871. A. ROLLETT. Hermann's Handbuch d. Physiol., 4, 1880. C. BIZZOZERO. Arch. It. Biol., 1882, 1883. HAYEM. Arch, de pliysiol., 1883. Gaz. med., 1883. HEDIN. Strass. Arch. f. Physiol., 1890. E. A. SCHAFER and A. GAMGEE. Schafer's Text-Book of Physiology, i. 1898. H. F. HAMBURGER. Osmotischer Druck u. lonenlehre. Wiesbaden, 1901-5. R. HOBER. Phys. Cliemie der Zelle u. der Gewebe, 2nd ed. Leipzig, 1906. F. WEIDENREICH. Die roten Blutkb'rperchen-Ergebnisse. Merkel and Bonnet, 1903-4. GRAWITZ. Klin. Path, des Blntes, 1902. ENGEL. Leitfaden z. klin. Unters. des B lutes, 1902. FOA. Arch. d. scienze med. Turin, 1906. Recent English Literature : W. MYERS. The Causes of the Shape of Non-nucleated Red Blood Corpuscles. Journ. of Anat. , xxxiv. 3, p. 351. A. GAMGEE. On the Behaviour of Oxy haemoglobin, etc., etc., in the Magnetic Field. Proc. Roy. Soc., Ixviii. 450, p. 503. J. HALDANE. The Colorimetric Determination of Haemoglobin. Journ. of Physiol., 1900-1, xxvi. 497. G. N. STEWART. The Conditions that underlie the Peculiarities in the Behaviour of the Coloured Blood Corpuscles to certain Substances. Journ. of Physiol., 1900-1, xxvi. 470. S. PESKIND. Notes on the Action of Acids and Acid Salts on Blood Corpuscles and some other Cells. Amer. Journ. of Physiol., 1903, viii. 99 and 404. G. N. STEWART. The Behaviour of Nucleated Blood Corpuscles to certain Haemolytic Agents. Amer. Journ. of Physiol., 1903, viii. 103. G. T. .KEMP. Relation of Blood Plates to the Increase in the Number of Red Corpuscles at High Altitudes. Proc. of the Amer. Physiol. Soc. (Amer. Journ. of Physiol.), 1902, vi. p. xi. G. T. KEMP and 0. 0. STANLEY. Some New Observations on Blood Plates. Proc. of the Amer. Physiol. Soc. (Amer. Journ. of Physiol.), 1902, vi. p. xi. C. C. GUTHRIE. The Laking of Dried Red Blood Corpuscles. Amer. Journ. of Physiol., 1903, viii. 441. G. N. STEWART. The Influence of Cold on the Action of some Haemolytic Agents. Amer. Journ. of Physiol., 1903, ix. 72. 122 PHYSIOLOGY CHAP, iv E. T. REICHEUT. Quick Methods for Crystallising Oxyhaemoglobin. Anier. Journ. of Physiol., 1903, ix. 07. P. B. HAWK. On the Morphological Changes in the Blood after Muscular Exercise. Amer. Journ. of Physiol., 1904, x. 384. P. P. L.VIDLAW. Some Observations on Blood Pigments. Journ. of Physiol., 1904, xxxi. 464. C. E. HAM and H. BALEAN. The Effects of Acids upon Blood. Journ. of Physiol., 1905, xxxii. 312. S. PESKIND. Ether-laking : A Contribution to the Study of Laking Agents that Dissolve Lecithin and Cholesterin. Amer. Jonrn. of Physiol., 1905, xii. 184. C. G. DOUGLAS. A Method for the Determination of the Volume of Blood in Animals. Journ. of Physiol., 1905-6, xxxiii. 493. E. W. REID. Osmotic Pressure of Solutions of Haemoglobin. Journ. of Physiol., 1905-6, xxxiii. 12. T. W. CLARKE and W. H. HURTLEY. On Sulph-haemoglobin. Journ. of Physiol., 1907-8, xxxvi. 62. H. C. Ross. On the Death of Leucocytes. Jonrn. of Physiol., 1908, xxxvii. 327. H. C. Ross. On the Vacuolatiou of Leucocytes and the Liquefaction of their Cytoplasm. Journ. of Physiol., 1908, xxxvii. 333. CHAPTER V THE BLOOD : PLASMA CONTENTS. 1. Different methods for separation of blood plasma from corpuscles. '2. Histogenic substances or proteins of plasma : tibrinogen, serum globulin, serum albumin, sero-mucoid. 3. Nitrogenous histolytic products of plasma. 4. Fatty substances. Carbohydrates and their derivatives. 5. Inorganic substances. Blood gases. 6. Theory of Coagulation : (a) conditions of blood coagulation ; (b) disintegration of corpuscles as cause of coagulation ; (c) fibrinogen as fibrin generator ; (d) analogies between blood coagulation and curdling of milk ; (c) importance of time in coagulation ; (/) thrombin and uucleins as coagulating substances ; (f Paraglobulin. Magnesium sulphate is added to saturation tu a measured quantity of blood serum. The fluid i> vigorously shaken, the precipitate in the form of a white paste, finely granulated, is collected on a filter and washed with saturated solution of MgSO 4 , to remove, the albumin. If the precipitate left on the filter is coloured, it is dissolved in a dilute solution of MgS0 4 or NaCl, and reprecipitated as before. This operation is repeated several times, and then completed in the manner described for the estimation of fibrinogen. Estimation of tier urn Albumin. The serum saturated with magnesium sulphate, from which the paraglobulin has been removed by filtering, can be used again for the quantitative estimation of serum albumin. This can be precipitated by the addition of a small amount of - 5-l per cent of acetic acid. To purify it, dissolve again in water, and reprecipitate with solution of ammonium sulphate. The further treatment is the same as that described above for filn-inogen. Serin is, however, more frequently calculated by difference, as follows : In one portion of serum the paraglobulin is estimated by the preceding method, and in a second portion, equal to the v THE BLOOD: PLASMA 129 tir.-t, the total weight of the proteins coagulated by alcoliol or by heat. The percentage amount of serum albumin can lie calculated from the difference between the two value:-. Estimation of Sero-mncoicL I. To prepare and simultaneously estimate r-t-ro-mucoid, Zanetti used the same method Morner employed for ovo-niucoid. The proteins are first precipitated from a given amount of blood serum diluted with t\vo volumes of 10 per cent NaCl solution, by coagulation, after previous acidification with acetic acid. The filtrate is evaporated on the water bath to a reduced volume, and is then treated with alcoliol. To purify the precipitate obtained, which consists of sero-mucoid, it is again dissolved in water, and reprecipitated with alcohol. This operation is repeated five, or six times, till a very slightly coloured precipitate is obtained, which can be collected on a filter that has been previously dried and weighed. After repeated washing with ether, the substance is dried in vacua over sulphuric acid till the weight is constant. The sero-mucoid appears as a light straw-coloured powder. It is somewhat hygroscopic, dissolves in warm water, and gives all the reactions of mucoid substances. Its property of reducing Fehliug's solution after previous boiling with hydrochloric acid, led Zanetti to term it gluco-protein. III. The various proteins differ little iu their percentage com- position, and are probably derived from the molecular complex into which the different nuclei or groups of atoms have entered in different relations. In fact, when broken up by steam at high pressure, or by prolonged boiling with dilute alkali or mineral acids, they invariably yield the same products, viz. ammonia, hydrogen sulphide, and a series of amino-acids, among which tyrosine, leucine, and asparaginic acid are always present. Since tyrosine is a compound of the aromatic series, and leucine and asparaginic acid are two bodies of the fatty series, we may conclude that atomic groups of both series enter into the protein molecule. Within the body, however, in consequence of the metabolic- activity of the living elements of the tissues, the proteins give rise to a large number of decomposition products, which are either simple waste products, destined as such to be eliminated by the various excretory organs, or products of internal secretion, destined to fulfil other functions and to undergo further trans- formations before they are eliminated. For the most part these consist of the constituents of urine, which are excreted by the kidneys, among the most important being creatine, creatinine, uric- acid, hippuric acid, carbamic acid, and urea. All these are nitro- genous compounds, and are therefore derived from retrogressive or katabolic metamorphoses of the proteins. As these waste products are promptly eliminated as fast as they reach the blood plasma, they can obviously exist there only in very minute quantities. As a matter of fact, urea and ammonia are the sole constituents of urine that can be isolated from blood serum, urea only in an amount of which the maximum does not exceed 0'05 per cent (I. Munk), ammonia in an average amount of 0'79 mgrin. to each 100 grms. of blood (Beccari). Creatine and uric acid are found in much smaller quantities ; hippuric VOL. I K 130 PHYSIOLOGY CHAP. acid least of all, since, as will be shown later on, tin.; greater part at any rate is formed by a synthetic process in the kidneys. Under pathological conditions, however, when the renal function is profoundly affected or abolished (uraemia), as also in grave alterations of the blood (leucaemia), besides these nitrogenous products others, which are normally present in the urine in exceedingly small quantities, e.g. the xanthine bases (Scherer), can be demonstrated in the serum. IV. Besides the nitrogenous compounds, neutral fats are found in the blood serum, emulsified to minute drops which can readily be extracted with ether. The amount, which under normal con- ditions does not exceed 0'1-0'2 per cent, increases conspicuously after a fatty meal, giving a milky appearance to the serum, and it may reach or exceed 1 per cent of the total quantity of blood (Kohrig) ; whereas in the fasting state only minute traces remain (Pfeiffer). It is thus obvious that the fats of the blood are derived principally from the fatty substances taken in with the food. In certain morbid conditions, however (alcoholism, diabetes, diseases of the bone marrow), the amount of fat in the blood plasma may increase so rnuch that the serum assumes a milky aspect (lipaemia) as after a meal that has been rich in fats. It is therefore probable that the fat of the blood is, even under normal conditions, derived to a lesser extent from what is eliminated or liquefied from the adipose tissues. In addition to neutral fats, blood serum contains soaps, lecithin, and cholesterin (Hoppe-Seyler). These form part of the products of pancreatic digestion, hence they also come in part from the digestive canal. A third group of organic substances also found in serum are conventionally comprised under the term carbohydrates : glucose, glycogen, lactic acid. There is yet another reducing substance, which is not fermentable ; it contains phosphorus, is capable of extraction with ether, and gives all the reactions of jecorin (Jacobson). Lastly, there is a small quantity of animal gum (Freund). The most important of all these substances is certainly glucose, which originates partly direct from the food, partly from the digestive transformation of alimentary starch, partly from the glycogen of the liver and muscles. The quantity of glucose in the blood is independent of the nature of the food, because, as we shall see later, nearly all the glucose absorbed from the intestine is stored up in the liver in the form of glycogen (liver starch). The amount of glucose found in normal human blood varies from O'lO to 0'15 per cent (Otto); but under abnormal conditions it may reach 0'3 per cent or more. It is at a maximum during post- digestive absorption in the blood of the portal veins, while during inanition it is most abundant in the blood of the hepatic veins. V THE BLOOD: PLASMA 131 The small amount of glycogen that can lie demonstrated in blood serum (Pavy) probably derives from the disintegration of the leucocytes, which, as stated, contain a certain amount of it. The constant presence of lactic acid in blood serum is in- dependent of the ingestiou of carbohydrates, while it is, on the contrary, partly dependent on the flesh food. The amount of lactic acid found in the blood of dogs during absorption after a full meat meal, may amount to 0'3-0'5 per cent, while after forty-eight hours' starvation it diminishes to 017 per cent (Gaglio). Lactic acid, as we shall see, is one of the decomposition 1 products of proteins, elaborated either by the blood corpuscles or by the living elements of the various tissues. V. The mineral constituents of blood plasma occur partly in the form of free salts, partly in combination with the proteins, from which they cannot be separated by simple dialysis. What the true physical and chemical conditions within the plasma the reciprocal relations and the fixed or labile bonds between the various mineral constituents on the one hand, and the various proteins on the other may be, is one of the most difficult problems in the chemical physiology of to-day, and its solution is the aim of various physico-chemical researches, of which this is not the place to speak. If combustion is employed to isolate the inorganic matters from the dry residue of serum, the ash will be found to contain a large amount of sulphates, derived from the combustion of the sulphur of the proteins, which are not among the mineral con- stituents of true plasma. In the same way, if care be not taken before the serum is incinerated to remove the lecithin by ether, there will, owing to combustion of its phosphates, be an excessive increase in the phosphates of the ash. Setting aside for these reasons the sulphates and phosphates found in the ash of serum, the results of the different analyses made for man and for the other mammals harmonise perfectly for the rest of the constituents, as appears from the following table : In 1000 parts of serum. Human Blood Pin's Blood Calf's Bloor! Average nf tli-' (C. Schmidt). (Bunge). (Bunge). three analyses. K,0 . 0-394 0-273 0-234 0-300 Na.,0 4-290 4-272 4-351 4-304 Cl . 3-612 3-611 3-717 3-646 CaO . 0'155 0-136 0-126 0-139 MgO. 0-101 0-038 0-045 0-061 8-552 8-330 8-473 8-450 132 PHYSIOLOGY CHAP. These figures show that sodium chloride is by far the most abundant constituent of the ash of serum. It is held in simple solution in the plasma or in the form of highly unstable compounds, for when serum is dialysed in distilled water, osmotic equilibrium between the two fluids is soon arrived at in regard to the chlorine. The greater part of the sodium of the ash exists in the form of bicarbonate (Gtirber) in the plasma, a lesser amount being com- bined with phosphoric acid in the form of di-sodic phosphate. It should be noted that potassium salts predominate in the corpuscles, sodium salts in the plasma. The osmotic pressure of plasma depends largely upon the sum of the inorganic matters which it contains ; it is, as we shall see, of great importance in the metabolic exchanges between corpuscles and plasma, and between plasma and tissues. The blood gases, as a whole, represent a very small part of the weight of the blood (0'10-O15 per cent). They are oxygen, carbonic acid, nitrogen, and also argon. The two first occur principally in combination, the two last in simple solutions. Nitrogen and argon are not known to fulfil any function in the animal economy; on the other hand (as we shall find in discussing the Chemistry of Respiration), oxygen and carbonic acid are of capital importance. Here we must confine ourselves to stating that the combinations which they form of oxygen with haemoglobin, and of carbonic acid with haemoglobin and the alkalies, are very unstable, so that it is possible with the vacuum to separate and estimate volumetrically the whole of the gases contained in the blood. VI. After ascertaining the several constituents of the blood corpuscles and blood plasma, it is easier to marshal the data referring to the solution of the problem of Blood Coagulation, a problem which is indeed one of the most difficult in physiological chemistry. Although this problem has of late years been treated with extraordinary acumen by a number of observers (e.g. A. Schmidt in particular), we cannot at present claim to have established any theory that is universally acceptable in all its details. In studying the phenomena of coagulation it is well to treat the different questions and problems involved as if each were separate and distinct in itself. (.) The first problem that presents itself is why, i.e. under what conditions, the blood, which remains fluid so long as it circulates within the vessels, coagulates spontaneously soon after it leaves them. This question was attacked by Hewson in the eighteenth century, while Briicke solved it more completely in 1857. Clotting does not depend upon the cooling of the blood, for when frozen before coagulation, it is found on thawing still to be fluid, and clots soon after in the usual manner. Cooling, therefore. v THE BLOOD: PLASMA 133 retards coagulation ; as shown by the fact that when the shed blood is warmed to the ordinary temperature of the animal (37-3S C.) it x;lots more rapidly (Hewson). Coagulation does not depend on the quiescence of the blood drawn from the vein, for some of the blood in the dog's heart 13 hours after death (Hewson), and the whole of a dog's blood 6|-7| hours after death by asphyxia, is found to be fluid. Again, the blood in a tortoise heart that has been ligatured or excised, and kept at a temperature of approximately zero, is found to be fluid 7-8 days after (Briicke). Nor, again, does coagulation depend on contact with the air or its oxygen, for the blood received under a bell-jar filled with mercury coagulates, and the blood of a tortoise does not clot after injection of a considerable quantity of air into its vessels (Briicke). Contact with the normal, living walls of the vessels inhibits coagulation of the circulating blood, while the injury or death of the vascular endotheliurn, or the introduction of any foreign body into the vessels (e.g. a needle pushed through the heart of a living tortoise), make the blood coagulate (Briicke). When the blood is received directly into a vessel greased with vaseliu, or under oil, it neither adheres to it nor clots, nor does it on stirring with a well-greased glass rod. On the other hand, it coagulates readily when stirred with a rod that has not been greased, or when any foreign body is introduced which the blood can adhere to. It is therefore highly probable that the circulating blood remains fluid because its morphological elements do not adhere to the normal endotheliurn of the vessels, and that a thrombus is formed whenever such adhesion becomes possible by degeneration of the endotheliuni (Durante) or other morbid lesions of the internal walls of the vessels and heart, as, e.g., in phlebitis, endocarditis, eudarteritis, atheromatosis (Freund, 1886). (6) The second question to lie solved is the determination of the immediate cause of coagulation, i.e. why the simple adhesion of certain elements of the blood to foreign bodies, or to the injured endotheliurn, should give rise to the formation of fibrin. In this connection we have a series of striking observations, which show plainly that the formation of the fibrin clot is intimately bound up with the functional alteration or destruction of the formed elements of the blood, more particularly of the leucocytes, which, as we have seen, are very unstable, and easily damaged by every imaginable external physical influence. Simple contact with foreign bodies, to which they may adhere, is sufficient to provoke secretion in the plasma of substances able to produce clotting. This theory, proposed by Addison (1841) and Beale (1864), was clearly demonstrated for the first time by Mantegazza (1876). Wherever a thrombus is produced within the vessels or the heart, 134 PHYSIOLOGY CHAI-. the fibrinous clot is seen under the microscope to be infiltrated with more or less altered leucocytes. If a silk thread is introduced into the interior of a large vein, and carefully drawn out after some time and investigated under the microscope, a fine coagulum will be seen to have formed round the thread, which is denser in the places where the leucocytes enclosed among the filaments are most numerous (Mantegazza). When the coagulation of a small drop of blood plasma is watched under the microscope, the fibrin threads of which it is constituted are often seen to spread out like rays from a centre, which is formed by a leucocyte or a collection of disintegrated platelets (Ranvier, Hayem, Bizzozero). On separating the plasma of horse's blood by cooling, and filtering it through a triple layer of filter-paper, it can be obtained entirely free of formed elements. In this case it will be seen that the plasma left at the temperature of the environment may remain fiu id even after twenty-four hours. But if even a nominal amount of a watery extract of leucocytes, or a little blood serum containing leucocytes, be added, clotting at once occurs (A. Schmidt). Certain morbid pathological transudations behave exactly like the cell-free plasma, e.g. hydrocele, or pericardial fluid, which are free from formed constituents, and are of a similar composition to plasma. Left to themselves, they remain fluid for an unlimited time, but coagulate so soon as a little blood clot or serum is added (Buchanan, 1835). When entirely freed from corpuscles by prolonged and energetic centrifuging, the plasma separated from peptonised blood not only does not coagulate spontaneously, but will not do so on the addition of water, or when a stream of carbonic acid is passed through, as is the case with peptonised plasma not wholly deprived of leucocytes. But if a little clump of leucocytes and platelets obtained by centrifuging be added, coagulation at once occurs (Fano). ' The theory of Hayem and Bizzozero to the effect that coagula- tion depends essentially on injury or destruction of the blood- platelets, does not contradict the preceding theory, by which it is associated with the injury or destruction of leucocytes. Assuming (as seems probable from the researches of Lilienfeld, referred to in the last chapter) that blood-platelets are derived from leucocytes and represent the mass of their nuclei, the two points of view are quite in harmony, and may be combined and enlarged into a single theory. A. Petrone has recently discovered that the blood coagulates firmly and rapidly in the early stages of pyrogallic acid poisoning (1 per cent solution introduced per rectum for dogs and rabbits), while the platelets are not injured, and even appear to increase, the erythrocytes only suffering marked deterioration. The analytical investigation of this complex intoxication has, however, v THE BLOOD: PLASMA 135 been too incomplete to make it the basis of a theory so opposed to observations and experiments conducted on simpler and, therefore, more convincing lines. Lymph contains neither erythrocytes nor platelets, as shown by Fauo, and yet it coagulates. (c) The third point in the theory of coagulation is to determine on which or what chemical constituents of the blood the formation of fibrin depends, since it is insoluble and cannot, therefore, pre- exist as such in the blood. It was pointed out by Hewson (1770) and by (i. Mliller (1832) that the mother-substance of fibrin is derived, not from the corpuscles, but from the constituents of the blood plasma. Hewson was the first to obtain salted plasma comparatively free from corpuscles, and noted that it formed a white clot on the simple addition of water. Joh. Miiller succeeded in filtering frog's blood, in which coagulation had been retarded with a sugar solution, thus separating the corpuscles that remained on the filter from the colourless plasma of the filtrate, and obtained in the latter a clot of pure fibrin. The first, however, to demonstrate that coagulation is a change of chemical state in a substance of the plasma which he termed fibrinogen (which is found isolated in the transudates already referred to, and mixed with serum globulin and serum albumin in the plasma), was A. Schmidt. He assumed that two elements enter into the composition of fibrin : fibrinogen (the fibrinogenic substance), and paraglobulin (fibrinoplastic substance), explaining by this the observations of Buchanan, as cited above. Subsequently, however, it was shown by Hammarsten (1875), and confirmed by others, that paraglobulin takes no part in the formation of the clot, since the blood contains an equal amount both before and after coagulation, and since a solution of pure fibrinogen obtained from salt plasma can yield a fibrinous clot 011 adding a little watery extract of serum, which is quite free from paraglobulin. (d) A fourth problem : granted that fibrinogen is able to produce fibrin by a change in its chemical state, it must be determined in what this change consists. This question is attacked in the later work of Hammarsten, Arthus, Lilienfeld, Carbone and others. Some hold the coagulation of blood to be a phenomenon analogous to the curdling of milk. The substance derived from the corpuscles which excites coagulation splits up the fibriuogen into two new globulins thrombosin, which is insoluble, and changes into fibrin : and fibrinoglobulin, which remains in solution in the plasma. During this splitting of the fibrinogen, i.e. liydration, the chemical association of water with the proteins occurs. A. Schmidt has recently shown that pure horse's plasma, dried before coagula- tion, weighs about 2 per cent less than an equal amount of the same plasma dried after coagulation. 1:56 PHYSIOLOGY CHAP. The presence of a certain amount of soluble and readily ionisable lime salts in the plasma seems essential to coagulation, or to the transformation of the soluble thrombosin into fibrin, which precipitates as a clot. The reason why oxalates and sodium fluoride, even in small doses, render plasma incoagulable lies in the fact that they precipitate the calcium salts dissolved in the plasma, and thus hinder the conversion of thrombosin into fibrin by combination with the lime salts. Fibrin accordingly would be a compound of calcium with thrombosin, and comparable as such with the soluble curd which is a calcium compound of paracasein. Just as milk casein splits under the action of the rennet ferment into paracasein and a special albuniose, so fibrinogen splits up during blood coagulation, two-thirds of it forming thrombosin and one-third fibrinoglobulin. As paracaseiu in combination with lime forms curd, so thrombosin in the same combination produces fibrin (Arthus, Lilienfeld). To this ingenious parallel between the clotting of blood and that of milk, the objection has been raised that even if fibrin always contains lime, it is no richer in lime than is the fibrinogen ; hence it cannot be assumed that fibrinogen takes up lime from the plasma in its transformations into fibrin. Others on the contrary affirm, perhaps more reasonably, that coagulation is produced by a simple splitting of the fibrinogen into a less soluble body that precipitates (fibrin), and another that is soluble (fibrin globulin) which remains in the serum ; the presence of lime seems indispensable, not to this reaction directly, but to the production or the activity of the fibrin ferment. In any case it is undeniable that the presence of calcium in plasma is essential to coagulation, even if its precise action is still undetermined. (e) Another question to be solved relates to the chemical form of the calcium when it participates as an indispensable factor in coagulation. Some hold that it intervenes as a phosphate, more correctly as a tricalcic phosphate, and think that as it is insoluble in \vater, it remains dissolved in the plasma in combination with the proteins ; Arthus, however, demonstrated that insoluble lime salts are useless, and that the presence of soluble salts is essential. Sabbatani further demonstrated that it is not merely the soluble salts, but also the ionisable salts of calcium that are always present in plasma, which are indispensable. It therefore appears probable that calcium intervenes in coagulation in virtue of its characters and chemical properties as a kat-ion, combining with those elements that have the function of an-ions, perhaps with the leuconuclein of Lilienfeld, which we shall discuss later. The quantity of calcium ions adequate to produce blood v THE BLOOD: PLASMA 137 coagulation, unlike that required in milk coagulation, is minimal, but under uniform experimental conditions it is constant ; we thus have a critical value for the concentration of Ca-ions, below which the blood remains indefinitely liquid. On the one hand, accordingly, all physical or chemical agents that lower the concentration of the Ca-ions of the blood below the critical value provoke incoagulability ; on the other, all those agents which raise it above the said value favour coagulation. Among the former are cold, high molecular concentration, small doses of reagents which form almost insoluble salts with calcium (oxalates, fluorides, soaps, carbonates, alkaline pyrophosphates), moderate doses of reagents which with lime form simple salts that are sparingly soluble (di-sodic sulphate and phosphate, sodium bicarbonate), small doses of reagents which with lime form compounds that are little ionisable (tri-sodic citrate, sodic meta- phosphate) ; among the latter are heat, dilution with water, addition of small quantities of ionisable lime salts, addition of reagents that liberate thecalciuin from its insoluble or little dissociable compounds. On the other hand, the addition of small quantities of calcium to normal blood invariably diminishes coagulability (Sabbatani, Eegoli), and it was only the inexact interpretation of certain experiments of Dastre and Hammarsten that led people for some time to believe that it was increased by the same ; the addition of a moderate quantity much delays coagulation ; large doses entirely prevent it (Home). From all these results it appears, in regard to the concentration of Ca-ions in the blood, that we must assume an optimum value for coagulation (lying between the limits of the physiological variations which calcium presents in normal blood), and two critical values, minimal and maximal, above and below which the blood no longer coagulates. The addition of lime increases coagulation only when the blood is deficient in it. (/) Next comes the question of determining by what process the injury or dissociation of blood corpuscles leads to the breaking- up of librinogeu into fibrin and fibrin-globulin. A. Schmidt and his school (Dorpat) treat blood coagulation as a process determined by an enzyme which they call thrombin, which is derived from the blood corpuscles, particularly from the leucocytes and platelets. In the normal state these contain, not the ferment, but a zymogenic substance, pro-thromlin, which on injury or destruction of the corpuscles gives rise to the ferment proper, thrombin. This can be extracted either from defibrinated blood or from blood serum, by absolute alcohol, which precipitates the protein matters with the ferment. The ferment can be extracted from the mass of the well-dried and pulverised clot by making a watery extract. 138 PHYSIOLOGY each. To the first add 3 - l c.c. distilled water, to the second 3 c.c., to the third 2 - 9 c.c., to the. fourth 2'8 c.c., to the firth 2'7 c.c., and to the sixth 2 - 6 c.c. Then let three drops of defibrinated blood fall into each test-tube, agitate the mixtures and centrifuge. It is known experimentally that the NaCl solution isotonic with mammalian blood, thus diluted, fluctuates between 0'55 and 0'65 per cent. Pour about 8 c.c. of the following solutions of NaCl into six more test-tubes similarly numbered 0-62, 0-61, 0'60, 0'59, 0-58, and 0'57 per cent. Then, as in the first series, let three drops of defibrinated blood fall into each tube, .and shake. After two hours the erythi", \ti-s will have sunk to the bottom in all the VOL. I La 148 PHYSIOLOGY CHAP. teM-t ill"--. In lln' firs! series tin' fluid will In- red in .-ome, colourless in others. When, ,-.r.- lo which JM, 3 - 0, and 2 - 9 c.c. of water have l>een added, and colourless in the rest, the result works out as follows :- The mixture of f> c.c, serum + 2'9 c.e. water shows diffusion of l)lood pigment, while 1 the mixture of 5 c.c. serum+2'8 c.c. water remains colourless. On examining the second set of test-tubes, the Huid is seen to )>e tinted in a saline solution of 0'58 per cent and in the. weaker solutions, while the contents of the tubes with the stronger solutions, 0*59, O60 ])er cent, etc., remain untinged. _;<) _j. -i-*, The mixture of ~> c..c. serum + - ..," \\ater is therefore isotonic with a solution of NaCl at =0'585 per ecu!. 4 Accordingly in calculating the NaCl solution isotonic with the normal non-diluted serum, the following equation may l>e employed : f) : 5 + 2-85 = 0-58.-) : z, 5 + 2-85x0-585 whence il follows that : x =0*92 per cent. . In this case the blood serum is isotonic with a NaCl solution of O92 per cent. Raoultfs Method. Tlie determination of osmotic pressure by this method is more easily carried out. The apparatus commonly adopted is that of Beckmann (Fig. 43). It consists essentially of a glass vessel 6', which, is filled with a free/ing mixture (crushed ice and salt), a test-tube B introduced to a certain depth in the vessel C, and a longer tube A fitted with a lateral tube r which also dips into the tube B. The tube A is closed with a cork, through the centre of which passes the special Beckmann thermometer D (or an ordinary thermometer with a scale divided into hundredths of a degree) and platinum wire F, which is bent into a loop at its lower end. This platinum wire, which is intended to stir the fluid contained in the glass tube A, is automatically set in motion by a little motor driven by water or electricity or other power. In using the apparatus the vessel G is first filled with the freezing mixture, then a few c.c. of serum are poured into the tube A till the bull) of the thermometer is covered, when the stirrer F is set in motion. The mercury column of the thermometer must be watched until, after sinking, it rises again, and then remains for a few seconds at the temperature attained, which is the freezing-point of the liquid. In practice, it is usual to assist the free/ing and rise of the thermometer by dropping a small crystal of ice into the liquid through the lateral tube E. When the freezing-point, which Eaoult indicates by A, has thus been obtained, it is easy in the case of blood serum to calculate the solution of NaCl with which it is isotonic. If, /-.(/., with ox serum, A =0'55", when the 1 per cent solution is found to free/e at - 0'588, it can easily be calculated that the NaCl solution isotonic with the serum under examination is equal to 0-90 per cent. Hafiiiatocrite Method. This method (adopted by Hedin, Gartner, Daland, Koppe, Eykman, Gryiis, Manca) is founded on the property possessed by the red corpuscles of varying their volume with the variations of the solutions with which they are in contact. On studying the action of solutions of different concentration of the same substance (provided there is no destructive action on the erythrocytes), these become smaller in more con- centrated solutions, larger in more dilute solutions ; their volume is constant only in a solution which is weaker than that which crenates the corpuscles, ami stronger than others which make them swell out. On experimenting with various substances these' observers found for each a solution at which THE BLOOD: PLASMA 149 U the volume of the corpuscles remains unchanged. These solutions, taken as isotonic, correspond exactly with those found by the methods of Hamburger and Raoult. Tin- apparatus employed is practically the same as that described on p. 104, Fig. 31, save that the capillary tube (haematocrite), 7 cm. long, is divided into 100 parts, finished at one end by a funnel- shaped swelling. To ascertain the solution of NaCl that is isotonic with that of mammalian blood serum, the first step is to aspirate into different haematocrites a quantity as equal as possible, and containing about - 02 c.c. of blood corpuscles. The haematocrites are placed in the horizontal supports represented in the said figure, and centrifuged till the column of erythrocytes becomes regular and constant, while the height they reach is simultaneously noted. Next, to the free portion in each haematocrite is added, by means of a Pravaz' syringe or a measuring pipette graduated in hundredths of c.c., a given quantity (0'2 c.c.) of the various solutions of serum, diluted in the same way as those em- ployed in examination of the osmotic pressure _ of the serum according to Hamburger's method. The erythrocytes are mixed with the solution by means of a fine needle, care being taken to close the capillary end of the haematocrite with the finger, and they are then again centrifuged for an hour and a half, until the level of the stratum of corpuscles remains constant. This is easily ascertained when, on reading the height of the stratum of erythrocytes, at intervals of a few minutes' centrifuging, they show the same figure. On then examining with a lens the several columns of fluid corpuscles, that solution is to be taken as isotonic in which the column in the haematocrite is level with the original. If none of the columns are exactly in this condition, the isotonic solution is intermediate between the tube in which the corpuscles are either just shrunk or just swollen, i.e. the first is just hypertoiiic, the second is just hypotonic. Method of Electrical Conductivity. The cryoscopic method enables us to study the mole- cular concentration of the blood and the serum, that of electrical conductivity permits us to study the electrolytes they contain. Accord- ing to Arrhenius, electrical conductivity is due to the dissociated portion of the electrolytes, to the positive and negative ions (kations and aiiions), their number 'and their velocity in the fluid. It, varies with everything that causes the concentration and mobility of the ions to vary, such as the chemical nature of the electrolytes, their molecular concentration, the presence of anelectrolytes and colloids, the temperature. The electrical conductivity (K) of a solution is the reciprocal of the resistance (r), measured in ohms, which it offers, to the passage of the electrical current. Resistance is measured by Kohlrausch's method with the apparatus shown VOL. I L & FIG. 43. Beckmann's Cryoscope. 150 PHYSIOLOGY CHAT. in the schema of Fig. 44. Hen- 1 is I lie source of the induced current, r tin- resistance of the liquid to be determined, R a resistance expressed in ohms, Tn telephone, x a contact that slides along a metal wire pq, which is kept tense and parallel with a scale divided into 1000 parts and one metre in length. This arrangement constitutes the so-called Wheatstone Bridge, and no electrical current passes through the telephone T, i.e. it remains silent, when the contact x divides the wire pq into two parts, px and xq, such that the resistances of px, xq, r and .R are related thus : r : R ~-=px : xq. FIG. 44. Diagram of apparatus used for determining the electrical conductivity of fluids. It is easy to find this point x by holding the telephone to the ear and sliding the contact along the wire pq, the above ratio enabling us to calculate the = 1000 : required resistance, as 2 = R, and noting that - IQQQ-px The resistance capacity ((7) of the cell containing the fluid to be examined is found by determining the resistance (;?) which it offers with a given solution N of known conductivity (), e.g. KC1 r^, and calculating C=x2. In all other fluids to be examined in the same cell the specific electrical conductivity Q is calculated on the basis of this value, x -~ The conductivity at 25 of the serum of healthy human blood (Viola) calculated in ohms (.cxlO 5 ) oscillates between 1128 and 1232. That of the blood is much less, and at the moment of clotting it presents a rapid diminution (Galeotti). Besides osmosis and electrical conductivity, we must briefly consider the physiological importance of another physical property, v THE BLOOD: PLASMA 151 the viscosity of blood plasma, to which no one had called attention previous to the interesting work of Albanese, On the Influence of the Composition of Nutritive Fluids on the Activity of the Isolated Frogs Heart (1893). Let it be said in the first place that the viscosity of a homo- geneous fluid, such as plasma or blood serum, is due to the internal friction between its molecules and those of the solvent (water), and of the bodies in solution or in pseudo-solution (colloids), whether or no these are electrolytes, dissociated or non-dissociated ; and that in heterogeneous fluids, such as the blood, entire or defi- brinated, the viscosity is largely augmented by the presence of the corpuscular elements. It varies considerably with temperature, and is measured by special instruments called viscorneters. The measurement is based on the time which a known volume of fluid takes to pass along a capillary tube. When the pressure under which the fluid passes, and the dimensions of the capillary tube, are known, it is possible to obtain absolute values (p) of viscosity ; but often it suffices to obtain the relative value (r/) by comparison with that of another fluid, e.g. distilled water. Hiirthle suggested another method by which it is possible to determine the viscosity of circulating blood in the living animal ; but better results are obtained experimentally in vitro and with blood serum. Bottazzi found the value ?/ at 15 C. for dog's serum = 2-0233- 2-0486, and at 39 C. = 1-84-1-87 ; Mayer at 40 C. for mammalia obtained values that oscillated between 1*41 and T95. In the dog the viscosity of serum and defibrinated blood is as 1 : 5 (Bottazzi). The viscosity of blood determined by Albanese with Ostwald's viscometer (v. Grundriss der allgemeinen Chemie, Leipzig, 1890) is approximately equal to that of a 2-3 per cent solution of gum arabic. He believes in a certain constant ratio between isotonicity and isoviscosity ; but this seems improbable, since the fluids within the body are isotonic but not isoviscous. The physiological importance of viscosity depends principally on the great resistance which it entails on the blood passing through the capillaries, and on the corresponding effort that must be made by the heart. But it is probable that the high viscosity of the blood and the presence of colloids influence some chemical reactions in a way that does not obtain in pure water or in fluids of less viscosity ; and this notwithstanding that the diffusion of . crystalloids in colloid solutions is effected with the same rapidity as in water. From this it appears that a fluid, in order to be completely physiological, that is to say, indifferent and innocuous to the living tissues, must, besides being isotonic and isoconductive, be also isoviscous, i.e. it must possess a degree of viscosity equal to that of blood plasma, 152 PHYSIOLOGY CHAP. VIII. In order to appreciate the importance of the functions of the blood in the animal economy, it will he well to examine briefly the most important consequences of haemorrhage and transfusion of blood. (a) Loss of blood, however produced, results in a weakening of the body in correspondence with the amount of blood lost. A haemorrhage of 30 grms. is dangerous or deadly in the new-born infant, of 180-200 grms. in a child of one year old, of half the blood (2000-2500 grms.) in the adult. Women appear to stand loss of blood relatively better than men, because they have the power, being subject to periodical haemorrhages (menstruation), of reform- ing it more quickly. In consequence of the relative speed at which blood forms again it is possible to obtain a greater volume of blood by repeated bleeding than was originally present in the animal, without causing its death. Vierordt (1854) was one of the first to investigate the effect of bleeding upon the number of red corpuscles, and he found that they diminished continuously with successive bleeding, and that death occurred when the relative quantity of blood corpuscles fell below a certain limit, which differs for different individuals. If the loss of blood is not pushed so far as to kill the animal there will be an increased influx of lymph into the blood, by which more water, with its contained salts and proteins, is taken up from the tissues. The neo-forrnation of erythrocytes takes longer. A con- dition of hydraemia then obtains, associated with oligocythacmia and leucocytosis, due to the increased passage into the blood of lymph which carries a greater number of leucocytes with it. All these facts (and others which we shall discuss in speaking of haemato- poiesis) have been substantially confirmed by recent observers (Hayem, Bizzozero, Golgi). (&) The effects of transfusion of blood are more important. We must distinguish between direct transfusion, from vein to vein, and indirect, viz. the injection of extracted and defibrinated blood, between homogeneous transfusion of the blood of the same species and heterogeneous transfusion of the blood of animals of other O species. Direct homogeneous transfusion is readily tolerated. According to the observations of Worm-Miiller the normal quantity of serum in an animal can be increased to 83 per cent, in consequence of the great adaptability of the vascular system, without serious symptoms. But if the increase of blood is carried too far, so that its quantity is doubled, alarming symptoms occur, and when the increase is raised to 145 per cent the animal dies from interstitial haemorrhage, in consequence of vascular laceration. If a certain quantity of blood is transfused, there will be a rapid return to the normal, owing to increased elimination from the kidneys. The proteins of the plasma are also reduced (if less v THE BLOOD: PLASMA 153 rapidly) to the normal quantity, owing to their conversion into nitrogenous waste products. A marked increase of urea in urine is actually observed during the first (2-5) days after transfusion (Worm-Muller, Landois). The erythrocytes diminish far more slowly, so that the blood for about a month is richer in corpuscles (polycythaemia) and haemoglobin (Panuni, Lesser, Worm-Muller). The diminution of the corpuscles is due to the breakiug-up of their constituents, as manifested in a moderate increase in the urea excreted daily by the kidneys, and the bile pigments secreted by the liver (Landois). It is remarkable that a rapid consumption of transfused blood is observed even during inanition. In a dog that has been sub- jected to a prolonged fast, periodical transfusion does not hinder progressive wasting of the body (Luciani). Indirect, as well as direct, homogeneous transfusion is tolerated (provided the amount be not excessive), although defibrinated blood contains a considerable quantity of thrombin and of co- agulative nuclein- containing substances. Panum succeeded in replacing almost the whole of a dog's blood by other homogeneous, defibrinated blood, without injury to the animal. In this case, no plethora is produced ; the transfused blood is supported well by the new individual, and shows no abnormal tendency to degenerate. This indicates homogeneous transfusion as a rational measure to avoid the danger of death in severe haemorrhage. Since, however, in many cases death ensues not from deficiency of the nutritive matters of the blood, but because the necessaryrnechanical conditions of the circulation are wanting, it is simpler in practice to replace transfusion of blood by intravenous injection of physiological saline (0~9 per cent), as suggested by Kronecker. The salt water is of itself capable of maintaining the circulation, giving time for new blood to form, and thus averting the danger of death from haemorrhage. Transfusion of heterogeneous blood is dangerous to the life of the animal even when it is administered in moderate doses. It provokes fever with haemoglobinuria (Ponfik), due to dissolution of erythrocytes (Landois) ; capillary embolism, due to agglutination of foreign blood -corpuscles (Albertoni) ; fibrinous clotting, extra- vasation of blood, diarrhoea, cholaemia, and bile pigments in urine, etc., all effects of the destruction of blood-corpuscles. This toxic and specifically haemolytic action of the blood of an animal in regard to the blood of another animal of a different species is exhibited regularly, but in varying degrees, in the different species. Thus the blood of certain fishes, e.g. of the eel and lamprey, is excessively toxic to mammals (A. Mosso). In order to kill a rabbit, it suffices to inject 0'5 grm. of eel's blood for each kgrm. of the rabbit's, into the circulation or peritoneal cavity ; while to produce the same effect with duck's blood, 7 grrns. are required ; with dog's blood 40 grms. per kgrm. (Hericourt and Kichet). 154 PHYSIOLOGY CHAP. The haeraolytic or globulicidal toxic action of heterogeneous blood depends rather upon the plasma than on the blood-corpuscles. Approximately the same effect is produced by injection of heterogeneous serum (Landois). (c) The capacity of the blood, or serum, to destroy the foreign cellular elements that penetrate it, is intimately connected with another, and, from the medical point of view, i'ar more important of its properties viz. destruction of certain pathogenic bacteria ; this constitutes a natural defence of the body against special infectious diseases, and is even more important than the phagocytosis attributed to the leucocytes. Fodor (1887) and then Nuttall and Flugge (1888) were the first to demonstrate the bactericidal properties of the blood of living healthy animals. H. Buchner (1889) showed that these depend on the very unstable proteins of the plasma, which derive from the metabolic activity of the leucocytes or other cells, and which he designated by the name of alexins (from d/\.e>/o-is, defence). He found that the serum lost its bactericidal property on simple dialysis with water, but not with physiological salt solution. By this treatment the serum only loses its salts ; yet after the restoration of its original molecular concentration it does not recover its bactericidal activity. This is perhaps due to the fact that the salts before dialysis are in some way bound up with the proteins, which association, on account of its great instability, cannot be reinstated when once disturbed by dialysis. The serum also loses its bactericidal effect on warming to 55 C. for an hour or to 52 C. for six hours, a fresh proof of the great lability of the alexins. The bactericidal action of one kind of blood is not common to all other species, nor does it extend to all bacteria, only to certain of them. Thus, e.g., the serum of human blood contains alexins against the bacteria of typhoid and cholera, while it has less effect upon Staphylococcus pyogenes, and none on streptococci and the diphtheria bacilli and anthrax ; the serum of the rabbit and dog will kill typhoid bacilli, while the serum of the calf and horse have not this power (Buchner) ; the serum of the rat kills anthrax bacilli, while the serum of mouse, guinea-pig, rabbit and sheep has no bactericidal effect upon them (Behring). Yet more wonderful is the fact, which has been recognised for some time, that recovery from certain infectious diseases is followed by immunity to them. Behring and Kitasato (1890) discovered the cause of this phenomenon to be that the said infections develop as an after-effect (in the blood of those persons who survive them) a previously non-existent property of rendering the bacterial toxins innocuous. They further showed that if the serum of an individual who has become immune to any given infection be injected into other individuals in sufficient doses, v THE BLOOD : PLASMA 155 it is capable of transmitting to those persons immunity to that- same disease, to which they would previously have been liable. These i'acts cannot be understood without admitting that in such cases the infective agent sets up a formation of special protective substances or antitoxins in the body, which are then poured into the blood, and which apparently consist in certain special modifica- tions in the proteins of the plasma. We cannot, however, enter at length upon this interesting subject without transgressing the limits of a Text-book of Physiology. BIBLIOGRAPHY For Classical Bibliography of the Blood, see H. XASSE. Blut. Wagner's Handworterbuch d. Physiologic, pp. 75-220. Bruns- wick, 1842. For Modern Literature, besides recent books on Chemical Physiology (see p. 39 et scq,), the two following monographs may profitably be consulted : A. SCHMIDT. Zur Blutlehre, Leipzig, 1892. Weitere Beitrage zur Blutlehre, Wiesbaden, 1895. R. v. LIMBECK. Klinische Pathologic des Blutes, Jena, 1S96. For Physico- Chemical Theory of Solutions, Molecular Weight, and Osmotic Pressure, see : K. NASINI. Analogia tra la materia allo stato gassoso e quella allo stato di soluzione diluita. Gazz. chimica It. xx. 1890. T. GARELLI. Pesi molecolari. Enc. chini. Unione tip.-editr. torinese, 1894-95. H. J. HAMBURGER. Die osmotische Spannkraft in den medicinischen Wissen- schaften. Virchow's Arch. 140, 1895. Osmotischer Druck u. lonenlehre. Wiesbaden, J. F. Bergmann, 1901. For Bibliography of Concentration and Osmotic Pressure of Blood Plasma and Resistance of Corpuscles, see H. KOPPE. Uber den Quellungsgrad der rothen Blutscheiben durch aquimolecu- lare Salzlusungen, und iiber den osmotischen Druck des Blutplasmas. Du Bois- Reymond's Arch., 1895. J. WINTER. De la concentration moK-culaire des liquides de 1'organisme. Arch. de physiol. de Brown-Sequard, tome viii. 1896. G. FANO e F. BOTTAZZI. Sur la pression osmotique du serum du sang, et de la lymphe en differeiites conditions de 1'organisme. Archives ital. de biologic, tome xxvi., 1896. G. MANCA. La Legge dei coefticienti isotonici uei globuli rossi del sangue conser- vato fuori dell' organismo. Arcliivio di Bizzozero, vol. xx. , 1896. T. CAEBONE. Contribute allo studio della coagulazione del sangue. Memorie della R. Accademia di Scienze, Lettere ed Arti in Modena, Sezione Scienze, serie in. vol. iii., 1900. L. SABBATAXI. Funzioue biologica del calcio. Parte seconda : II Calcio-ione nella coagulazione del sangue. Memorie della R. Ace. delle Sc. di Torino, serie n. tomo Iii., 1902, pag. 213-257. E. GARDELLA. Azione anticoagulante degli anioni in rapporto alia diluzioue del sangue. Archivio di fisiologia, vol. ii. , 1905. G. BUGLIA. Azione anticoagulante dei cationi in rapporto alia diluzioue del sangue. Archivio di fisiologia, vol. iii., 1906. G. GALEOTTI. Ricerche sulla couduttivita elettrica dei tessuti animali. Lo Sperimentale, anno lv., 1901. G. VIOLA. Ricerche elettro-chimiche e crioscopiche sopra alcuni sieri umani nor- mali e patologici. Rivista veneta di sc. med., anno xviii., 1901. F. BOTTAZZI. Ricerche sull' attrito interno (viscosita) di alcuni liquid! organic! < di alcune soluzioni acquose di sostanze proteiche. Archivio ital. di biol. , tome xxix. (1898), Principii di Fisiologia, vol. i. Elementi di chimica fisica. Milano, Societa editrice libraria, 1906. 156 PHYSIOLOGY CHAT, v P. MOKAWITZ. Ergebnisse d. Physiol., 4. Jahrg, 1905. (This syntlietic review of the Chemistry of Blood Coagulation comprises 490 references to papers.) Recent English Literature : T. G. BRODIE. The Immediate Action of an Intravenous Injection of Blood Serum. Journ. of Physiol., 1900-1, xxvi. 48. A. E. WRIGHT. On a Method of measuring the Bactericidal Power of the Blood for Clinical and Experimental Uses. The Lancet, 1900, No. 4031, 1556. A. E. WRIGHT. On the Measurement of the Bactericidal Power of Small Samples of Blood under Aerobic and Anaerobic Conditions, etc. etc. Proc. Roy. Soc. Ixxi. 54. A. E. WUIGHT. The Action exerted on the Coagulability of the Blood by an Admixture of Lymph. Journ. of Physiol., 1902, xxviii. 514. J. BARCUOFT. The Estimation of Urea in Blood. Journ. of Physiol., 190-3, xxix. 181. E. P. BAUMANN. The Effect of Haemorrhage upon the Composition of the Normal Blood, etc., etc. Journ. of Physiol., 1903, xxix. 18. S. G. HEDIN. On the Presence of a Proteolytic Enzyme in the Normal Serum of the Ox. Journ. of Physiol., 1904, xxx. 195. R. BURTON-OPITZ. The Changes in the Viscosity of the Blood produced by Alcohol. Journ. of Physiol., 1905, xxxii. 8. R. BuRNET-OriTZ. The Changes in the Viscosity of the Blood during Narcosis. Journ. of Physiol., 1905, xxxii. 385. G. N. STEWART. The Influence of the Stromata and Liquid of Laked Corpuscles on the Production of Haemolysins and Agglutiuins. Amer. Journ. of Physiol., 1904, xi. 250 ; and 1905, xii. 363. R. T. FRANK. A Note on the Electric Conductivity of Blood during Coagulation. Amer. Journ. of Physiol., 1905, xiv. 866. J. MELLANBY. The Physical Properties of Horse Serum. Journ. of Physiol., 1906-7, xxxv. 473. W. H. HOWELL. The Proteids of the Blood with Especial Reference to the Existence of Non-Coagulable Proteids. Amer. Journ. of Physiol., 1906-7, xvii. 280. L. J. RETTGEU. The Coagulation of Blood. Amer. Journ. of Physiol., 1909, xxiv. 406. J. MELLANBY. The Coagulation of Blood. Jouru. of Physiol., 1909, xxxviii. 28. J. MELLANBY. The Coagulation of Blood, Part II. The Actions of Snake Venoms. Journ. of Physiol., 1909, xxxviii. 441. H. E. ROAF. The Osmotic Pressure of Haemoglobin. Proc. Physiol. Soc., Journ. of Physiol. xxxviii. 1. CHAPTEK VI THE CIRCULATION OF THE BLOOD : ITS DISCOVERY CONTENTS. 1. Physiological necessity for the circulation of the blood. Schema of cardio-vascular system. "1. Theory of Galen. 3. Discovery of the lesser cir- culation : question of the priority of Columbus, Servetus, and Vesalius. 4. Dis- covery of the general circulation by Cesalpinus. f>. Completion of the work by Harvey. 6. Discovery of the lymph circulation by Eustachius, Aselli, Pecquet, Rudbeck, Bartholiu. 7. Discovery of the capillary system, and direct observation of the circulation by Malpighi. 8. Microscopic observations of the phenomena of circulation : Spallanzani, Poiseuille, R. Wagner, etc. 9. Discovery of diapedesis of blood-corpuscles and migration of leucocytes : Waller, Addison, Reckliiighausen, Cohnheim. Bibliography. THE Blood, in order to fulfil its physiological task as centre and agent of the metabolic exchanges of the whole body, must be in perpetual motion within the vascular system which contains it. If the blood remained stagnant, that portion of it which lay within the capillaries of the pulmonary system might indeed become saturated with oxygen, but would be unable to conduct it to the parts where it is required, i.e. to the parenchyma of the organs ; on the other hand, the portion contained in the capillaries of the aortic system would become charged with carbonic acid which could not be exhaled from the body. The blood of the capillaries leading to the portal veins would become charged with the nutritive materials taken up from without, but would be unable to reach the organs that require feeding ; while the products of consumption, again, would accumulate in these organs, since they could not reach the organs of excretion. I. Owing to the intensity of metabolism necessary to the maintenance of the principal vital functions, especially in the higher animals, the arrest of the movements of the blood leads in a few moments to death from asphyxia of all the tissues. The vascular system is therefore provided with a pumping apparatus, which serves to keep the blood in continuous rapid movement in all parts of the body. If we reduce the cardio-vascular system to a schema (Ing. 45), we may distinguish anatomically a central organ, and the arterial, venous, and capillary systems : physiologically, a right or venous, 157 158 PHYSIOLOGY CHAP. cc and a left or arterial heart, connected by a system of vessels running centrifugally and another running centripetally, which are closed, and comnmnicate by a capillary system. The system of the lesser, or pulmonary, circula- tion unites the ventricle of the right with the auricle of the left heart ; the system of the great, or aortic, circulation connects the ventricle of the left heart with the auricle of the right. The auri- culo- ventricular orifices and the orifices of the two big arteries which arise from the ventricles are provided with valves ; the orifices of the great veins, which open into the auricles, have no valves, although on the other hand valves are plentiful along the course of the veins. The importance of the several parts of the circulatory system is very different. Only the capillary portion serves the physiological uses of the blood. The arteries and veins are only paths to con- duct the blood to the seat of its activity, whence it is again returned to the heart. The heart is the motor, a perfect pumping machine to circulate the blood, emptying its contents into the arteries during systole, filling itself again with blood from the veins during dia- ' The discovery of the CirCllla- - Kic. 4. r i. Diagramof cardiovascular system. Ke PHYSIOLOGY CHAP. of the migratory cells, but his work was ohviously (as stated by P. Heger) " the true introduction to that associated three years later with the name of Cohnheim." We must now briefly describe the facts that can be observed without difficulty either in the mesentery or the tongue of the frog, after it has been paralysed with curare, or its spinal cord destroyed, when a certain amount of neuro-paralytic dilatation of the small arteries is produced. When the peritoneum is exposed to air, the circulation in the peritoneal vessels exhibits a marked retardation after about an hour, so that (with a magnification of 200 to oOO diameters) the corpuscles can not only be seen distinctly circulating in the capillaries and veins, but also in quicker motion within the small arteries. This delay has no sooner begun than a partial block and Flo. 49. Cohnheim's apparatus for studying the course of the circulatory phenomena in inllummution of frog's peritoneum. accumulation of corpuscles will be observed in the capillaries^ which gradually disappears in some places to reappear in others. In the small veins the most conspicuous feature is the im- mobilisation of the leucocytes on the internal walls of the vessels. As they leave the capillary network, they advance with a rotary motion along the wall of the vein, and become fixed in contact with those that are already immobilised. Little by little they cover the entire internal surface of the small veins, forming a hollow cylinder of motionless leucocytes surrounding the cylinder of moving erythrocytes. On continuing to observe the leucocytes clinging to the walls of the small veins and capillaries, it is possible in about two hours from the beginning of the experiment to catch the corpuscles in flagrante, in the very act of traversing the vessel walls to penetrate into the meshes of the connective tissue or into a lymph sheath, or the surface of the serosa. Here and there on the outside of the vessel an irregular lump of protoplasm is seen, which forms a sort of hernia, and is continuous with the iutra vascular portion of the protoplasm of the corpuscles. The external portion of the corpuscle becomes vi CIRCULATION OF KLOOD : ITS DISCOVERY 177 gradually larger, while the iutravascular portion still keeping its round shape continuously diminishes in volume, till at last it appears only as a mere shining point, and eventually disappears altogether. The extravasated leucocyte is then seen completely free from the vessel ; it resumes its circular shape, and remains motionless. The direct observation of diapedesis can be facilitated by staining the leucocytes of the blood with niethylene blue or other colouring matters introduced into the dorsal lymph-sac of the frog the method of Cohnheim. Recent researches have left no doubt that the diapedesis of leucocytes is an active phenomenon, intimately connected with their amoeboid mobility. The extravasation of red corpuscles (the true haemorrhagia per diapedesin, as divined by the ancients) is, on the contrary, a passive process, depending either on rise of intra- vascular pressure or on nutritional disturbances and lowered resistance of the capillary walls. In the frog's peritoneum the extravasation of the erythrocytes (from the capillaries rather than from the veins) is first noticed after several hours, and becomes conspicuous only twenty-four hours after the beginning of the experiment, in the capillary uetw r ork where the circulation is at a standstill and the block of corpuscles is greatest. This observation led Cohnh( j im to the opinion that the leucocytes penetrate through tiny pre-formed stoniata in the vessel wall, by which the erythrocytes can escape only when the openings are abnormally enlarged by the active work of the leucocytes. The opinion that prevails at present, however, is that no pre-formed stoniata exist, and that the emigration proceeds by temporary openings, excavated by the pseudopodia of the leucocytes at the junction of the liistologic il elements of the venous walls or capillary endothelia. The erythrocytes, owing to the softness and elasticity of their protoplasm, pass readily (perhips even passively) through the openings excavated by the leucocytes, as through a network. It is still doubtful if corpuscular extravasation (whether active, as for the leucocytes, or passive, for the erythrocytes) is to be regarded as a pliysiolog cal phenomenon, exaggerated under abnormal conditions of inflammatory irritation, or as an emphati- cally pat/iolor/ical phenomenon. E. Hering adopted the former opinion, on the strength of the following experiment. He injected a finely pulverised aniline pigment into the blood of an animal, and after some time examined the hepatic lymph, when he found numerous leucocytes as well as erythrocytes impregnated with pigment, but no free granules of pigment in the lymph plasma. From this he con- cluded that under normal conditions also certain leucocytes (and possibly erythrocytes as well) migrate from the vascular system VOL. I N 178 PHYSIOLOGY CHAP. by diapedesis, and penetrate through the lacunae of the plasma into the lymphatic system. ]>e this as it may, it is certain that diapedesis proceeds tumultuously during inflammatory irritation, and gives rise to the phenomenon of suppuration at the focus of inflammation. In order to complete the theory of corpuscular diapedesis we must further inquire why the leucocytes become stationary and adherent at the origin of the veins, and migrate from the vascular system. A satisfactory answer to this question can only be obtained from the interesting studies of Pfeffer on Chemotaxis, which were alluded to in Chap. III. (pp. 74-76). Leber was the first to regard the migration of leucocytes as a chemotactic phenomenon, caused by an attractive, or directive action exerted by the chemical products of the pyogenic or pus- producing microbes on the leucocytes. He extracted from the culture of Stapliylococcus pi/oyenes aureus a crystallisable substance, which he termed phlogosiu, and observed that some time after the introduction of a capillary tube filled with a solution of this substance into the anterior chamber of the rabbit's eye, a mass of leucocytes migrated from the pericorneal vessels. Lubarsch was able to show that living bacteria had a greater attraction for frog's leucocytes than those previously killed by heat. Massart and Bordet succeeded in showing that the same leucocytes are attracted by liquid cultures of different microbes (v. Fig. 19, p. 75, Staphylococcus pyogenes al~bus\ by inflammatory exudates, and by certain nitrogenous or phosphorus-containing waste products, e.g. leucin. They also discovered another im- portant fact : if the leucocytes are narcotised in the total narcosis of the animal by paraldehyde or chloroform, they are checked like amoebae in their active movements, and all emigration that might be going on from the vessels ceases entirely. This confirms the idea that the migration of the leucocytes is a process dependent on their excitability or amoeboid sensibility. In microscopic observations of the circulation in small vessels and capillaries, the transparency of the richly vascular organs of certain animals can be made use of. This is excellently seen in the frogs lung, by Holmgren's method (v. Fig. 48, p. 173). After em-arising the animal by the subcutaneous injection of a few drops of 1 per cent curare (sufficient to paralyse it) a lateral incision is made through the whole depth of the body wall, a little below the anterior limb. The lung inflated with air will usually protrude of itself from the opening. To avoid emptying the lung, which is useless for observation in the collapsed state, Holmgren employed a small caimula, which is introduced through the glottis, and attached by a ligature to the lower jaw. The end of the can nu Ja has two circular grooves in which is tied a l>it of frog's intestine into which the caimula had been introduced. Between the two grooves are two openings, into which air is blown so as to distend the intestine drawn over it. This dilates, and serves as a tampon, preventing the air of the lung from escaping through the space between the cannula and the glottis. A small rubber tube is fixed to the cannula, carrying at the other end a clip which is closed MI vi CIRCULATION OF BLOOD: ITS DISCOVERY 179 soon as the lung has readied the desired state of extension. To obviate the inconvenience due t<> tin- convex surface of the organ, Holmgren invented a little apparatus which consists of a special frog-holder, on which the animal can lie. It has an opening clo.-ed liy a glass plate, above which a second glass plate is fixed in a metal frame, which can be raised or lowered by a screw. The lung, suitably inflated, is brought between these two plates, its convex surface being flattened and adapted for observation by gentle pressure of the upper plate. Anot hei- admirable subject for the observation of the circulation, which was used more particularly by Cohnheim in his classical work on inflamma- tion, is the frog's mesentery (r. Fig. 49, p. 176). The experiment is carried out as follows : The ciirarised frog is laid on a cork plate, with a hole in its centre to correspond with the aperture in the stage of the microscope, to which the cork plate is fixed by clamps. Above the hole in the cork plate a ring, also cut out of cork, is fixed by pins, the. upper edge of which has a depression that serves to hold the bit of intestine fixed so as to stretch the mesentery. A lateral incision now has to be made in the frog's abdomen, avoiding the lateral vein, when a loop of intestine is carefully drawn out with forceps, and laid in the depression of the cork ring, so that the stretched mesentery lies taut over the aperture of the ring. This la-ings the part under examination to a higher level than the abdominal wound, otherwise it would become charged with blood and serum escaping from the wound. The above ring is not required for observing the circulation in the interdigital membrane or tongue of the frog, or in the tadpole's tail, etc., as these can be simply fixed to the cork plate, by pins. When the observation is to be prolonged for any length of time, it is necessary to prevent the parts from drying up, which is done by placing over them little strips of filter- paper soaked in physiological salt solution. The same method, with greater precautions in regard to moisture and temperature, will serve for examining the capillary circulation in warm-blooded animals, using, e.g., the mesentery of mouse, guinea-pig, etc. BIBLIOGRAPHY For the history of discovery of the Circulation of the Blood, the reader is referred to the two following monographs, which comprise an enormous amount of research in original texts, and a clear and impartial criticism of ancient and modern contributions to the literature of this vexed question : G. CEUADINI. Ricerche storico-critiche intorno alia scoperta della circulazione del sangue. Milan, Fratilli Richiedei, 1876 (333 pp.)- Difesa della mia Memoria intorno alia scoperta della circulazione del sangue, contro 1' assalto dei signori H. Tollin teologo in Magdeburg, e W. Preyer fisiologo in lena. Con qualche nuovo appunto circa la storia della scoperta medesima. Genoa, 1876. SIR MICHAEL FOSTER. History of Physiology. Cambridge, 1901. R. WILLIS. Preface to Syclenham Edition of Harvey's Works. London, 1878. M. ROTH. Andreas Vesalius Bruxelliensis. Berlin, 1902. For discovery of Lymph Circulation the fine article in Lipsius may be consulted : W. His. Uber die Eutdeckung des Lymphsystems. Zeitschr. f. Anat. u. Entwickelungsgeschichte, 1875. For discovery of Corpuscular Diapedesis, a complete account will be found in the following memoir : P. HEGER. Etude critique et exp. sur 1'einigration des globules de sang, envisages dans ses rapports avec I'inflanrmation. Brussels, H. Mauceaux, 1878 (116 pp.). For Phagocytosis and Clieniotropism of Leucocytes see : E. METSCHNIKOW. Lei.-ons sur la pathologic comparee de 1'inflammation. Paris, 1892. CHAPTER VII MECHANICS OF THE HEART CONTENTS. 1. Description of cardiac cycle or revolution. 2. Changes of ex- ternal form, of the internal cavity, of the position and volume of the heart in the different phases of its activity. 3. Mechanism of semihmar valves. 4. Mechanism of auriculo- ventricular valves. f>. Theory of so-called heart-sounds. 6. Variations of pressure within the auricles and ventricles during the cardiac cycle. 7. The diastolic aspiration ; various explanatory hypotheses. 8. Cardiac plethysinograms ; theory of active diastole. 9. Cardiograms ; theory of heart-beats or impulses. 10. Other mechanical effects of cardiac activity. 11. "Work done by the heart. Bibliography. THE continuous circulation of the blood from the arteries to the veins through the capillaries demands, as its first indispensable condition, a mechanism by means of which blood pressure is maintained high in the arteries and low in the veins, so that there is a considerable difference of pressure between the two parts of the vascular system. This mechanism is represented by the heart, which in its rhythmical movements drives as much blood through the aorta and pulmonary artery during systole, as it receives from the venae cavae and pulmonary veins during diastole. I. When the movements of the exposed heart are observed in the living animal, a series of phenomena, which are repeated at regular intervals, is witnessed. Each such cycle of movements is known as the cardiac cycle, or revolution. The duration of each cycle is exactly equal to the time interval between any two recognisable arterial pulses. This interval may be divided into three periods : in the first is the (normally synchronous) systole of the two auricles ; in the second, the (normally synchronous) systole of the two ventricles ; in the third, the pause or rest of the whole heart. For simplicity's sake, the first may be termed pre-systole ; the second, systole ; the third, peri-systole. The diastole of the auricles coincides with the commencement of systole, the diastole of the ventricles with the commencement of perisystole. The words avaroXri and Siaa-roKri from crv-a-TfXXeii', contrahere, and 5ia-crTi \\etv, distrahere, were first used by Galen. The term peri-systole for the resting period of the heart as a whole was introduced l.y Riolan (Encheiridium 180 CHAP. VII MECHANICS OF THE HEART 181 i, 1649), t licit of pre-systole by Spring, I860, who, however, intended 1o describe an imaginary active dilatation of the ventricle, immediately preceding systole. Normally the duration of presystole is much shorter than that of systole. With accelerated cardiac rhythm, i.e. when the period of the cardiac cycle decreases, perisystole, more particularly, shortens, and shows a tendency to disappear altogether ; the duration of systole, on the other hand, is either unchanged (Ludwig), or shortens only when there is an exag- gerated acceleration of rhythm (Donders). Presystole consists in a contraction of the mus- cular walls of the auricles, seen with the unaided eye to be peristaltic ; this peri- stalsis starts from the extreme end of the veins which open into the aur- icle, is propagated in the auricle from above down- wards, and extends as far as the auriculo- ventricular groove. The presystolic contraction diminishes the cavity of the auricles in every diameter, least, how- ever, in the longitudinal direction (Kiirschner). The striated muscle fibres with which the veins are provided in the vicinity of their openings into the auricle, and the arrangement of the mus- cular fibres of which the walls of the auricles con- sist (Figs. 50, 51), account for the changes in diameter exhibited in presystole. In systole, the ventricles seem on simple inspection to contract simultaneously at every point. Yet more delicate observation shows that the contraction here also is peristaltic, commencing at the auriculo-ventricular groove, when the presystolic movement has reached its maximum, and spreading thence to the apex with such velocity that the eye cannot follow it. Systole is accordingly only a continuation of the presystolic contraction wave, which Fir;. "iO. Human heart dissected after bulling, to show superficial muscular fibres, seen anteriorly. (Allen Thomson.) a', Aorta : >>', pulmonary artery cut short close to semilunar valves, to show anterior fibres of auricles : a, superficial layer of fibres of right ventricle ; b, that of left : c, c, anterior interventricular groove ; rf, right auricle ; , left ventricle ; <, <', posterior interventricular groove ; 4. Middle layer of muscular fibres, destitute of tendons, from left ventricle of . , , , , . human heart, after removing internal and lo Obtain tin- dead neart fixed in external layers. The form of the heart is diastole, it, must either not have entered em S!ft indicated ' ' fche " atmal the state of m/or mortis, or must already si/c. \ IN it Him) _. , ,, ,, ,_ have passed out oi it. Alter careluily removing the heart from the thorax, all the great vessels must, be made water-tight (by means of corks introduced into their lumen), with the excep- tion of the pulmonary vein and the vena cava superior, into which two glass tubes of the same calibre as that of the vessels must be introduced, and fixed by ligatures. Through these tubes the heart is tilled with water under a hydrostatic pressure of 50-100 mm. of mercury. The water enters by the great, veins into the auricles, and by the aorta into the coronary arteries, out of which it niters slowly through the cardiac walls. The heart is thus thrown into acute diastole, which is more pronounced than in life, and is left 6-8 hours in this state. It is then fixed with 96 per cent alcohol, which is passed through it for 3 to 4 hours under the same pressure as thai used for the water. To complete the hardening, absolute is substituted for the dilute alcohol, without any further pressure. Fixation in systole is effected by Hesse's heat method. The freshly extracted heart is" placed for an hour in a solution of potassium bichromate at 52 C., which throws it into a state of pronounced systole. Total systole of the human heart can only be demonstrated on the heart of a subject who has died suddenly, at the maximum of riijor mort-ix. Dissociation of the cardiac fibres is easy after treatment with ordinary nitric acid. This acid, however, shortens the muscle fibres, and throws the heart into more or less complete systole. Jn order to dissect out the heart VII MECHANICS OF THE HEAET 185 in diastole, it is necessary to prepare it with the acid under a pressure of 60 mm. mercury. This may be a complete success, but often fails, owing to the easy rupture of the heart, more particularly of the auricles. After submitting it to the action of the acid for about three hours, the heart is laid for several days in water, in which the connective tissue, softened by the acid, partly dissolves, and the rest can be readily separated from the muscular tissue. The muscle fibres can then be teased out without difficulty. A' B C' l-'ii;. ">"). A. SeL'tion tli rough heart of a criminal, fixed in systole, at limit of lower third of ventricles. A', Section through same heart, at limit of upper third. B, Section through heart of approxi- mately the same size as the preceding, fixed in diastole, at same level as A. 15', Section of same heart, at level of A'. All four figures are diminished by half. (Krehl.) The cavity of the left ventricle, seen in section, appears in systole as an irregular, somewhat star-shaped fissure, the centre of which corresponds with the conus arteriosus. This proves that the left ventricle is unable to empty itself completely, even in maximal contraction, so that a small quantity of blood is left in it, more especially in the space immediately behind the semilunar valves of the aorta. Its driving power depends mainly on the middle layer, contraction of which must produce a lengthening of the longitudinal diameter of the ventricle : this is, however, ISO PHYSIOLOGY CHAP. checked by the contraction of the external and internal coats, which compress the middle coat from above downwards. The longitudinal diameter of the left ventricle thus remains almost unaltered (Krehl). The cavity of the right ventricle is reduced in the maximal systole to a narrow space, which is curved towards the left ventricle on account of the convexity of the septum (Fig. 55). Owing to the absence of a middle layer, the longitudinal diameter of the right ventricle is bound to shorten, and contributes to the conical shape assumed by the heart, the apex becoming almost ventrical to the centre of the base. The numerous trabeculae with which the inner layer of the right ventricle is provided, and which connect its walls with the septum, must help to bring ventricle and septum together, and produce an almost complete occlusion of the cavity. Besides changes of form we have to consider those of position and volume, which are brought about in systole. It is easy to see by direct observation of the exposed living heart that the systolic shortening of its longitudinal diameter occurs not by lifting the apex, but by dropping the base. Haycraft (1891) demonstrated this on the closed thorax of c