General Physiology: An Outline of the Science of Life

The elementary constituent of all living substance and the substratum of all elementary vital phenomena is the cell. Hence, if the task of physiology lies in the explanation of vital phenomena, it is evident that general physiology can be only cell-physiology. Modern physiology has arrived at a point in its development where it must constantly extend its inquiries to the cell, the elementary substratum of all life that exists upon the earth's surface. It appears more and more clear that the general problems of life are cell-problems. This fact suggested to me the idea of examining from the cell-physiological standpoint these general problems, and the facts, theories, and hypotheses of the nature of life — subjects which thus far had never received comprehensive treatment — and thus outlining a field in which the various branches of special physiology might unite. In the present book, therefore, I have made an attempt to treat general physiology as general cell-physiology.

In dedicating this effort to the memory of Johannes Mtiller, I would express the obligation that we all owe to the work of our great master in physiology. But, more than all else, I would indicate Miiller's comparative-physiological standpoint, a standpoint that I have always strongly endeavoured to maintain in my own work. The comparative method of dealing with physiological problems, which Miiller's researches made so extremely fruitful, was unfortunately laid aside after his death, as physiology dealt more and more with the special problems of the human body. But it is now being shown constantly that the amount of material available for work in this latter field is too small in view of the variety of problems. Hence, if wrong and false generalisations

are to be avoided, and the science is to be allowed free development, it appears to me indispensable to return to Muller's method. For this reason I have dedicated the following pages to the memory of that great physiologist. The plan of the present book first assumed fixed form during a journey which I made in the year 1890 to different points on the Mediterranean Sea and the Red Sea for the purpose of making comparative-physiological researches. After my return my university lectures in Jena gave me an opportunity to present the collected material in connected form. But the greater part of the labour remained to be performed, and in the summer of 1892 I began the writing of the book. Although for nearly ten years I have been busy with the problems of general physiology and have endeavoured to contribute something to their solution, so much labour has been associated with the collection, examination, selection, completion, and arrangement of the much scattered material, that the book has progressed slowly — and with varied feelings on my part. I have often wondered whether the result would accord with the enthusiasm and love with which the task was undertaken. Only the criticism of my colleagues can decide this. It is not to be expected that a book which brings together for the first time in a unified form a mass of material hitherto regarded as heterogeneous, shall upon its first appearance pretend to completeness. I cherish no illusions that I have succeeded more than approximately. I am fully aware that many faults and errors must have crept in, and these I beg my colleagues in friendliness to correct.

It has afforded me especial satisfaction that one of my American colleagues, Professor Frederic S. Lee, of New York, in an address before the New York Academy of Sciences ('94), has developed simultaneously and independently the same ideas regarding the claims of modern physiology as are presented in detail by myself in the first chapter of this book. These ideas have also been expressed by me elsewhere, especially in an article in the Monist (Chicago, '94).

If a book is to reach a wide circle of readers, its language must be neither too technical nor too prosaic. I have endeavoured to comply with this requirement. I wished to write something that would appeal first to my fellow physiologists, and offer them, besides certain new facts and ideas, a summary of our scattered knowledge. But at the same time I wished the work to give to any interested scientific reader, whether a student of medicine, philosophy, botany, or zoology, an outlook over the problems, facts, theories, and hypotheses of life ; in other words, I wished to give him an introduction to general physiology, and thus afford him an idea of the important theoretical basis of his study. It is not easy to adapt oneself to these diverse aims. How far I have succeeded in doing this, only the judgment of the reader can decide. I bespeak his indulgent criticism.

I gratefully acknowledge my obligations to all my friends who have taken active part in the planning, developing, and completing of my task, and especially to Mr. Gustav Fischer, who has shown great liberality in the publication of the book. In offering the second edition of this work to the public, I feel it obligatory upon me to express my warmest thanks for the extremely favourable reception given the book upon its first appearance, by readers and especially by critics. I have been pleasantly surprised to realise — as I have been made to realise by personal talks, by letters, and particularly by the criticism of professional journals both at home and abroad — that the subject of general physiology excites active interest and receives abundant recognition in the circles not simply of theoretical natural science, but of practical medicine. It gives me much satisfaction to perceive in this a sign that the practical medicine of the day acknowledges the profound importance of a knowledge of the general physiology of cell-life for an understanding of the physiological and pathological phenomena exhibited in the cellcommunity of the human body. I am encouraged in this view by the gratifying fact that cell-physiological researches have increased greatly in number during the last few years. In this second edition I have endeavoured to note the more important of the later results. Unfortunately, because of lack of space, I have been obliged to treat many of these with more brevity than I desired, and to curtail the amount of attention given in the first edition to some of the older work. But by the introduction of a considerable number of new figures, and the replacement of certain faulty ones by better, I trust that the whole has been made more comprehensible. I cannot expect the present edition to be free from errors and faults ; but I trust that every critic will recognise the great difficulties involved in the treatment of such a large amount of material, and will be indulgent towards mistakes. I am sincerely grateful to my critics for having called attention to errors in the first edition. So

far as these were errors of fact, I have endeavoured to correct them ; so far as the points raised were based upon differences in conception, or points of view, I have conscientiously tried to allow them their full value. Translations of the book into English and Italian are in course of preparation, and a Russian edition has recently appeared. Since the latter was published wholly without my knowledge, and has not been seen by either my publisher or myself, I am forced to disclaim all responsibility for it.

I cannot forbear expressing my warmest thanks to Dr. Gustav Fischer, for the pains taken by him in issuing the present edition. The first comprehensive treatment of general physiology was contained in Claude Bernard's now classic Lemons sur les pMnom&nes de la me communs aux animaux et aiix vfyetaux, which was published in 1878-79. Since that time the only adequate work upon the subject has been Professor Verworn's Allgemeine Physiologic. The first edition of this book appeared in 1894. This was followed in 1897 by a second and revised edition. The work has been welcomed by European and American biologists, who have felt the need of a review and summary of the rapidly accumulating details of cell-physiology, and its ability and suggestiveness have been widely recognised. Many of the special views of the author have encountered opposition — a fact that perhaps is indicative of their value — yet, however much we may agree or disagree with him upon special points, we all must acknowledge his breadth and be grateful to him for presenting such a wealth of facts, and for pointing out so clearly the possibilities of research. With Professor Verworn's consent I have undertaken the task of translating and editing the book ; first, with the hope that in its English form it may enable English-speaking biologists and general scientific readers to realize more fully than before the wide scope of the science of Physiology ; and, secondly, because the book presents in a form convenient for the use of students suggestive and stimulating discussions of vital physiological questions.

A. The Earliest Times. B. The Period of Galen. C. The Period of Harvey. D. The Period of Haller. E. The Period of Johannes Miiller A. The Past Achievements of Physiological Research. B. The Relation of Psychology to Physiology. 1. The Question of the Limits of a Knowledge of Nature. 2. Physical World and Mind. 3. Psycho-monism. C. Vitalism. D. Cell-Physiology A. The Individualisation of Living Substance. 1. The Cell as an Elementary Organism. 2. General and Special Cell-constituents. 3. Multinucleate Cells and Syncytia. B. The Morphological Nature of Living Substance. 1. The Form and Size of the Cell. 2. Protoplasm, a. The Solid Constituents of Protoplasm, b. The Ground-substance of Protoplasm. 3. The Cell- Nucleus, a. The Form of the Nucleus. 6. The Substance of the Nucleus, c. The Structure of the Nucleus. C. The Physical Properties of Living Substance. 1. The Consistency of Living Substance. 2. The Specific Gravity of Living Substance. 3. The Optical Properties of Living Substance. D. The Chemical Properties of Living Substance. 1. The Organic Elements. 2. The

Chemical Compounds of the Cell. a. Proteids. b. Carbohydrates, c. Fats. d. The Inorganic Constituents of Living Substance. e. The Distribution of Substances in Protoplasm and Nucleus. A. Organisms and Inorganic Bodies. 1. Structural Differences. 2. Genetic Differences. 3. Physical Differences. 4. Chemical Differences. B. Living and Lifeless Organisms. 1. Life and Apparent Death. 2. Life and Death. A. The Ingestion of Substances. 1. Food-stuffs. 2. The Mode of Food-Ingestion by the Cell. B. The Transformation of In- gested Substances. 1. Extracellular and Intracellular Digestion. 2. Ferments and their Mode of Action. 3. Assimilation and Dissimilation, a. Assimilation, b. Dissimilation. C. The Output of Substances. 1. The Mode of Output of Substances by the Cell. 2. Secretions and Excretions, a. Secretions, b. Ex- cretions.

2. The Forms of Cell-division, a. Direct Cell-division, b. In- direct Cell-division. 3. Fertilisation. 4. The Development of the Multicellular Organism. A. The Forms of Energy. B. The Introduction of Energy into the Organism. 1. The Introduction of Chemical Energy. 2. The Introduction of Light and Heat. C. The Production of Energy by the Organism. 1. The Production of Mechanical Energy. a. Passive Movements, b. Movements by Swelling of the Cellwalls, c. Movements by Change of the Cell-turgor. d. Movements by Change of the Specific Gravity of the Cell. e. Movements by Secretion. /. Movements by Growth. </. Movements by Contraction and Expansion. 2. The Production of Light.

3. The Production of Heat. 4. The Production of Electricity. I. THE PRESENT CONDITIONS OF LIFE UPON THE EARTH'S SURFACE 273 A. The General External Conditions of Life. 1. Food. 2. Water. 3. Oxygen. 4. Temperature. 5. Pressure. B. The General Internal Conditions of Life. A. Theories concerning the Origin of Life upon the Earth. 1. The Doctrine of Spontaneous Generation. 2. The Theory of Cosmozoa. 3. Preyer's Theory of the Continuity of Life. 4. Pfl tiger's Idea. B. Critical. 1. Eternity or Beginning of Living Substance. 2. The Descent of Living Substance.

A. The Phenomena of Necrobiosis. 1. Histolytic Processes. 2. Metamorphic Processes. B. The Causes of Death. 1. External and Internal Causes of Death. 2. The Question of Physical Immortality. A. The Relation of Stimuli to Vital Conditions. 1. The Varieties of the Stimulus. 2. The Intensity of the Stimulus. 3. Trophic Stimuli. B. The Irritability of Living Substance. 1. The Conception of Irritability and the Nature of Reactions. 2. The Duration of Reactions. 3. The Conduction of the Stimulus.

A. The Actions of the Various Stimuli. 1. The Actions of Chemical Stimuli, a. The Phenomena of Excitation, b. The Phenomena of Depression. 2. The Actions of Mechanical Stimuli, a. The Phenomena of Excitation. 6. The Phenomena of Depression. 3. The Actions of Tlhermal Stimuli, a. The Phenomena of Excitation. 6. The Phenomena of Depression. 4. The Actions of Photic Stimuli. a. The Phenomena of Excitation. 6. The Phenomena of Depression. 5. The Actions of Electrical Stimuli, a. The Phenomena of Excitation. 6. The Phenomena of Depression. B. The Directive Effects of Unilateral Stimulation. 1. Chemotaxis. 2. Barotaxis. 3. Phototaxis. 4. Thermotaxis. 5. Galvanotaxis. C. The Phenomena of Over-Stimulation. 1. Fatigue and Exhaustion. Excitation and Depression. 3. Death by Over-stimulation.

A. The Metabolism of Biogens. 1. Biogens. 2. Biotonus. B. The Action of Stimuli upon the Metabolism of Biogens. 1. Changes of Biotonus upon Total Stimulation. 2. The Interference of Reactions. 3. Polar Changes of Biotonus and the Mechanism of Axial Orientation upon Unilateral Stimulation. A. The R61e of the Nucleus and the Protoplasm in the Life of the Cell. 1. The Theory of the Dominance of the Nucleus in the Cell. 2. Nucleus and Protoplasm as Links in the Metabolic Chain of the Cell. B. Derivation of the Elementary Vital Phenomena from the Metabolism of the Cell. 1. The Mechanics of

Cell-metabolism. a. Scheme of Cell-metabolism. b. The Mechanics of the Ingestion and Output of Substances. 2. The Mechanics of Changes of Cell-form, a. Growth as the Fundamental Phenomenon of Change of Form. b. Developmental Mechanics. c. Structure and Liquid. d. The Mechanics of Hereditary Transmission. 3. The Mechanics of the Transformation of Energy by the Cell. «. The Circulation of Energy in the Organic World, b. The Principle of the Transformation of Chemical Energy in the Cell. c,. The Source of the Energy of Muscle. d. Theory of the Movements of Contraction and Expansion.

III. THE CONSTITUTIONAL RELATIONS OF THE CELL-COMMUNITY . . . 567 A. Independence and Dependence of the Cells. B. Differentiation and Division of Labour among the Cells. C. Centralisation of Administration. IN every department of human culture a survey of its aims arid its achievements is desirable. Such a survey is, in a certain sense, a map ; at any moment it can serve for orientation, and can be combined with similar maps of other departments to form a harmonious and comprehensive idea of the world.

This desire is warranted especially in the natural sciences, the enormous development of which has influenced so powerfully the civilisation of the present century. Mankind has two potent needs, to the satisfying of which it is the purpose of science to contribute : a practical need, which is manifested in a search after a fitting and agreeable adaptation of the external conditions of life — the great development of modern technique and medicine bears witness to the efficiency of science in this respect ; and a theoretical need, which increases with civilisation and is manifested in a craving for causality or, in other words, a search after a harmonious idea of life and the world. Both needs are powerful, although they differ in intensity in accordance with individuality. Mankind has the right to demand of natural science that it shall never lose sight of its purpose and shall not mistake its attitude toward the other aspects of human life, a danger that, with the enormous extension of specialisation, is now growing imminent.

One-sided specialisation is continually falling into this error. It leads far into barren fields, gradually ceases to recognise neighbouring territory, and at last becomes incapable of co-labouring in the general tasks of science. It scarcely needs mention that it would be a mistake to lay aside specialisation altogether. Broadminded specialisation is one of the chief factors in the advance of knowledge ; without it, no general knowledge can be acquired. Bat a difference exists between special researches carried out for

the purpose of helping to solve a problem that concerns a practical or a theoretical need of life, and those that deal with chance or any external circumstance for the purpose of seeing what, if anything, will be the outcome. The former constitute true research, the latter, pastime. One-sided specialisation considers none of the great needs of mankind, and brings science finally to the unenviable standpoint of the famulus Wagner. It is absolutely essential to the advance of a science that in its special researches it keep clearly in view its general aim, its great problem ; investigation then becomes systematic. This is possible only when the investigator possesses such a survey as is referred to above.

Such an outlook over aims, paths, and achievements, in place of a mass of disconnected facts, is required, not by the individual investigator alone, but by every cultured man who would learn from science what is of value for the practical or theoretical needs of his life ; for science serves life, not life science. THE ancient Greeks associated with the word "<pv<n,<$" the conception of all living nature, a significance that finds expression in its purest form in the Homeric poems. Since that time the idea expressed by the word has undergone many changes. The original significance soon gave place to a more general one, and at the height of Grecian culture the Ionic philosophers, the oldest natural philosophers of Greece, were called "<t>v a-io\oyoi," the conception of </>uo-£9 being extended to all nature. Later, with the separation of physics as an independent science in its present sense, the conception became again narrow, but different from the original one, being limited to non-living nature and thus possessing a significance the exact opposite of the original one.

If the word (f>vcris be conceived in its proper original sense, the term " Physiology " expresses fully the essence of the science to -which the term is now applied, and it is unnecessary to replace it with the later word " Biology," with which at present very different ideas are associated. Physiology is the science of the phenomena of living nature, and, accordingly, its task is the investigation of life. In spite of the apparent simplicity of its task, the science has already laboured for centuries upon this problem. A little consideration will make its difficulties evident. It is only necessary to attach ideas to the expressions " life " and " investigation," which in this combination appear at first as empty words.

We will consider first the subject-matter of physiology, namely, life. The untrained person associates usually with this word a mass of ideas that concern phenomena of a secondary nature, because he thinks only of the remote results, constantly observed in daily life, of primary vital phenomena. With him life is characterised by various occupations, labours, pleasures, walking, travelling, reading, speaking, eating, drinking, etc., one or another activity appearing as the essential part of his own life according to his vocation and individuality : to one person, life is labour, to another a constant festivity. But the various occupations of daily life are combinations of a few primary vital phenomena. If the development of the conception of life be followed back to early antiquity, when mankind had no presentiments of all the occupations that accompany a highly developed culture, when he was unacquainted with fire, when he did not know how to make even the most primitive tools, the conclusion is reached that the conception sprang from the combination of a number of simple phenomena, which early man discovered by self-observation, especially those phenomena that are associated with evident movements, such as locomotion, breathing, nutrition, the heart-beat, and others. In fact, it is not difficult to analyse into their primary •constituents the complex occupations of our present life, and to recognise that its diversity is produced by various combinations of a few elementary phenomena, such as nutrition, respiration, growth, reproduction, movement, and the production of heat. If life be thus conceived as a sum of certain simple phenomena, the task of physiology is to determine, investigate, and explain the latter.

It must be remembered, however, that such a conception of life is limited to the vital phenomena of human beings, while the field of life is far greater. Animals and plants likewise exhibit vital phenomena, and it may be asked whether these latter are the same -as or different from the phenomena that prevail among men. It is evident that all living organisms must be included in the .sphere of physiological investigation, the flower and the worm equally with man. Hence the first duty of physiology is to mark out the field of the living, to determine what is living and what is not living — an undertaking that is more difficult than it appears. The conception of life has not always been the same. It has experienced fundamental changes in the course of the development of the human species. Formed first with respect to mankind, it was early extended to other objects. With primitive races, the conception was much wider than at present, and they termed living what is no longer regarded as such. With them stars, fire, wind and waves were beings endowed with life and mind, and they were personified in the image of man. The remains of these ideas are still found in the mythology of the classic and modern races. In the course of time the distinction between living and lifeless has been made constantly sharper, but even to-day a child regards •a steam engine as a living animal. The child is guided more or

less consciously by the same criterion as the primitive races, who from the fact of motion, considered as living the dancing flame of a fire or a moving wave. In fact, of all vital phenomena, motion is the one that gives most strongly the impression of living. It may be said that only primitive races and children are misled by the criterion of motion, and that the civilised and adult man, who is versed in a knowledge of life, is capable of deciding easily in any given case between the living and the lifeless. But this is not always true. For example, are dried grains living or lifeless ? Is a lentil that has lain unchanged in a chest for years living ? Scientific men themselves are not agreed upon this point. The lentil, when dry, does not show phenomena of life, but, if placed in moist earth, it can at any moment be induced to do so. It then sprouts and grows into a plant.

The decision between the living and the lifeless becomes, however, much more difficult with objects that are not commonly seen in daily life, e.g., certain microscopic things. Long observation and very detailed investigation are frequently required in order to> determine whether certain bodies that are found in a liquid by microscopic examination are living or not. If a drop of the dregs be taken from a bottle of weissbeer and examined with the microscope, it will be found that the liquid contains innumerable small pale globules, often clinging together in groups of two or three,, completely at rest so long as they are observed, and showing no trace of movement or other change. Very similar small globules, may be observed with a microscope in a drop of milk. The two kinds of globules can be distinguished from one another by strong magnifying powers only. No trace of vital phenomena can be found in either by the most patient and continued microscopic examination, yet the two objects are as widely different as a living organism and a lifeless substance ; for the globules from the beer are the so-called yeast-cells (Saccharomyces cerevisicz), the active agent in the fermentation of the beer and fully developed, unicellular, living organisms, while the globules from the milk are lifeless; droplets of fat, which, by their abundant presence and their reflection of light from all sides, give to the milk its white colour. As a counterpart to these two objects, we may consider a third. In the body-cavity of the frog on either side of the spinal column between the transverse processes of the vertebrae there lie small y yellowish-white masses.

If a bit of the contents of one of these be removed with a knife and placed with a drop of water upon a slide, and the whole be covered with a cover-glass, there may be seen with strong powers of the microscope a mass of minute granules and short rods of different sizes, which are trembling and dancing in constant motion, the smaller particles very actively, the larger ones more slowly. Every untrained person, brought before these three preparations and asked which of the three objects-

appears to him living and which lifeless, would invariably pronounce the yeast-cells and the fat-droplets lifeless, the dancing granules living ; but the latter are nothing more than minute calcareous •crystals, so light that they are put into trembling motion passively by the excessively delicate motion that the particles of every liquid possess. The manifestation of motion, which, because we see no external source, we are inclined to ascribe to an internal cause, here misleads to the assumption of life. Such examples may be found in unlimited number.

Hence, under certain circumstances it is not at all easy to distinguish the living from the lifeless, and it is accordingly clear that the first duty of physiology must be to inquire after the criteria of such a distinction, i.e., mentally to circumscribe the :subject-matter, life, in relation to non-living nature. Not less great are the difficulties that we meet when we •consider the second idea that is included in the task of physiology, that of investigation. What is meant by investigation or •explanation ?

Civilised man appears to be distinguished essentially from primitive races by a great desire, namely, that of seeking after the •causes of phenomena, or, in other words, a craving for causality. This longing in all things to ask " why," from a pure desire for knowledge apart from any practical aim, appears to be an acquisition of civilisation, and its origin and development can be seen clearly in children of a certain age. When we have discovered a cause for any phenomenon, the craving for causality in that respect is satisfied ; we have investigated and explained the phenomenon. This is true of investigation in all departments of science, of historical and philological science as well as that of nature, in so far as the development of the science has progressed beyond the .stage characterised by the mere accumulation of facts. But when we have discovered the immediate cause of any phenomenon, we have satisfied the craving for causality only relatively, for the cause itself is a phenomenon that must be explained. Thus gradually and systematically we put individual phenomena and series of phenomena into causal connection with one another, and constantly reduce larger and larger groups to their causes. Ultimately, however, the question arises how far this reduction may be carried .successfully. Is there a final cause for the phenomena, or may the reduction be continued to infinity ?