The Dynamics of Living Matter

THIS book owes its origin to a series of eight lectures delivered upon the invitation of Professor E. B. Wilson and Professor H. F. Osborn at Columbia University in the spring of 1902. The aim of the lectures was to give a presentation of my researches on the dynamics of living matter and the views to which they had led me. In preparing the book I have tried to give a somewhat more com- plete survey of the field of experimental biology than was possible in the lectures, without, however, trying to alter their character. In the introductory lecture use was made of my address at the Inter- national Congress at St. Louis.

To Dr. S. S. Maxwell, who has undertaken the main burden of reading the proof and preparing the index, and to Professor J. B. MacCallum, who also assisted me in the reading of the proof, my sincere thanks are due. 2. Reversible Enzyme Action — Lipase Action — Reversible Enzyme Action in the Carbohydrate Group — The General Occurrence of Protein-splitting Enzymes 9 (£) Further Remarks on the Significance of Oxygen in Life Phenomena . . 1 6 (<:) Death in Lack of Oxygen and the Protective Action of Oxygen . . 18

4. The Formation of Surface Films and Traube's Membranes of Precipitation - Overton's and Meyer's Work on Narcotics and the Nature of Surface Films . 38 5. Osmotic Pressure and the Exchange of Liquids between the Cells and the Sur- 6. Further Limitations of Traube's Theory of Semipermeability 45 THE ROLE OF ELECTROLYTES IN THE FORMATION AND PRESERVATION OF 1. On the Specific Difference between the Nutritive Solutions for Plants and Animals 2. Concerning a Theory of Irritability and the Role of Na, K, and Ca for Animal Life

— Rhythmical Contractions in Skeletal Muscle, in Medusa?, and the Ven- tricle of the Heart — Contact Irritability in Muscle — Analogies to the Role of Salts in Coagulation of Milk — Significance for the Understanding of Functional Nervous Diseases — The Action of Purgatives .... 78 3. The Reaction of Living Matter and the Role of Bicarbonates in the Preservation I. Effects of Heat — Upper Temperature Limit of Life — Influence of Reaction- velocity upon Biological Processes — Lower Temperature Limit — Other Biological Effects of Heat 106

?.. General Effects of Radiant Energy upon Living Matter — Chemical Action of Light 3. The Control of the Precision and Sense of Heliotropic Reactions in Animals . . 130 4. The Reaction of Animals to Sudden Changes in the Intensity of Light . . 135 1. The Specific Character of the Fertilizing Power of the Spermatozoon — Hybrid 2. Artificial Parthenogenesis and the Theory of Fertilization . . . 164 1. The Hereditary Effects of the Spermatozoon and Egg — The Prevailing Influence

of the Egg in the Early Stages of Development — Merogony — Toxicity of the Blood of Forms not closely Related — Mendel's Experiments . . .179 2. The Determination of Sex and the Secondary Sexual Characters .... 186 2. Heteromorphosis and Regeneration in Tubularia ....... 2OI 4. Regeneration and Heteromorphosis in Planarians . . . . . . 210 5. On the Influence of the Central Nervous System upon Regeneration and on Phe- 6. The Effect of Some External Conditions upon Regeneration and the Transforma-

7. The Role of Reversible Processes in Phenomena of Regeneration — The Distribu- tion of the Power of Regeneration in the Animal Kingdom . . . .218 IN these lectures we shall consider living organisms as chemical machines, consisting essentially of colloidal material, which possess the peculiarities of automatically developing, preserving, and reproducing themselves. The fact that the machines which can be created by man do not possess the power of automatic development, self-preservation, and reproduction constitutes for the present a fundamental difference between living machines and artificial machines. We must, however, admit that nothing contradicts the possibility that the artificial produc- tion of living matter may one day be accomplished. It is the purpose of these lectures to state to what extent we are able to control the phe- nomena of development, self-preservation, and reproduction.

Living organisms may be called chemical machines, inasmuch as the energy for their work and functions is derived from chemical pro- cesses, and inasmuch as the material from which the living machines are built must be formed through chemical processes. It is therefore only natural that the dynamics of living matter should begin with an analysis of the specific character of the chemical processes in organisms. It is neither our intention nor is it possible for us to give an exhaustive analysis, and we shall only go far enough to satisfy ourselves that no variables are found in the chemical dynamics of living matter which cannot be found also in the chemistry of inanimate nature.

The material of which living organisms consist is essentially col- loidal in its character. Graham introduced the discrimination between colloidal and crystalloidal substances : the latter diffuse easily, the former only with difficulty, or not at all, through animal membranes. The colloidal substances may be in solution or fine suspension, or they may appear in a jellylike or coagulated or precipitated form. In the former case wheje they are liquid we speak of sols, in the latter of gels. The structures which we find in living matter originate mostly through a gelation or coagulation of liquid colloids. We shall see in these lectures that liquefactions and gelations or coagulations may possibly play a great role in various physical manifestations of life ; but as the physics of colloids is still in its beginning, we must not be surprised that it is as yet impossible to carry its application to life phenomena very far.

As the chemical character of life phenomena and the physical struc- ture of living matter form the basis for the understanding of the dynamics of living matter, it is natural that they should be the starting-point in our lectures. As far as the specifically biological phenomena are concerned, namely, the phenomena of development, self-preservation, and repro- duction, it will be our aim to analyze them as much as at present pos- sible from a physicochemical point of view. It may perhaps be desirable before undertaking this task for us to state, as simply as possible, some of the individual problems that will present themselves for discussion, and the general method of their solution.

We know that the eggs of the majority of animals cannot develop unless they are fertilized, I.e. unless they are entered by a spermato- zoon. We do not know how the spermatozoon causes the egg to develop, but it is not to be expected that we shall gain an insight into these causes except by trying to imitate by purely chemical and physical means the effects which a spermatozoon has upon the egg. We shall see that this has been accomplished in some forms. Under ordinary condi- tions, the egg of Strongylocenlrotus purpuratus, a sea urchin of the Pacific coast, does not develop unless a spermatozoon enters it; but the fer- tilizing effect of a spermatozoon can be imitated in all essential details by putting the egg for a minute into sea water to which a certain amount of a fatty acid has been added and by subsequent exposure of the egg for about half an hour to sea water whose concentration has been raised by a certain amount. Similar results can be obtained in other forms.

From a given egg can arise a specific organism only, the morpho- logical and physiological qualities of which can be predicted with cer- tainty, if we know the organism from which the egg is derived. We call this fact heredity. Modern embryology has shown that the com- plicated adult forms develop gradually from simpler forms, and by following the development from the egg we readily understand how it happens that the adult form is so much more complicated than the egg from which it arises. The question which has recently puzzled biolo- gists is whether the egg has any structure which can be related to the adult form. This seems to be true in the eggs of some forms, to the extent at least that from the various regions of the egg somewhat differ- ent parts of the embryo arise. We do not know the causes which deter- mine this relatively slight differentiation inside of the egg, but we shall see that everything indicates that these causes may be of a simple physicochemical order. In studying the mechanism of heredity, it is perhaps of importance to realize that as far as the heredity of the earliest embryonic stage is concerned, it is almost, or exclusively, determined

by the egg. This is beautifully illustrated in the case of the hybridiza- tion of the egg of the sea urchin with the sperm of the starfish. The development of the pure breed of the sea urchin is after a certain stage (the gastrula stage) typically different from the development of the star- fish, inasmuch as the sea urchin's egg forms at that point a skeleton and goes into the characteristic pluteus form, while the starfish egg forms no skeleton, but undergoes a different development. When the sea urchin's egg is fertilized with starfish sperm, the egg always develops into a pluteus, never into the corresponding starfish form. If we exam- ine the adult forms of hybrids, however, we find that it makes no differ- ence which of the two forms furnishes the spermatozoon or the egg. This difference in the influence of the spermatozoon and egg upon the early embryonic and the adult form of the offspring is possibly due to a difference in the mass of the egg and the spermatozoon, the latter being as a rule much smaller than the former. As soon, however, as the embryo grows and its mass becomes large in comparison with that of the egg, the original difference in the hereditary effects of the two sex cells must diminish or disappear.

The foundations of a theory of heredity in the adult were laid by Gregor Mendel in his treatise on the hybrids of plants, and this theory is atomistic in its character. He showed that certain simple character- istics of plants, e.g. the round or angular form of the seeds of peas, or the color of their endosperm, must already be represented in the germ by definite determinants. His experiments on the hybridization of various forms of peas indicate that each hybrid contains two kinds of sexual cells, one possessing the determinants for the discriminating fatherly characteristic only, the other for the discriminating motherly characteristic. Both kinds of sexual cells seem to exist in equal numbers in such a hybrid. A similar fact has been discovered in other cases of hybridization, although it does not hold good for all cases. Hugo de Vries and others have begun to build up the physiology of heredity on the basis of Mendel's discovery.

It is obvious that no theory of evolution can be true which disagrees with the fundamental facts of heredity. It is the merit of De Vries to have shown that a mutation of species can be directly observed in cer- tain groups of plants, and he has further shown that the changes occur by jumps, not gradually. This fact harmonizes with the consequence to be drawn from Mendel's experiments that each individual char- acteristic of a species is represented by an individual determinant in the germ. This determinant may be a definite chemical compound. The transition or mutation from one form into another is therefore only possible through the addition or disappearance of one or more

of the characteristics or determinants. If this view can be applied generally, it is just as inconceivable that there should be gradual varia- tions of an individual characteristic and intermediary stages between two elementary mutations, as that there should be gradual transitions between one alcohol and its next neighbor in a chemical series. The fact that, as a rule, at a definite stage of development, larger masses of sexual cells are formed, is one of the automatic phenomena of development. The mechanism of this formation is unknown. Miescher tried to solve this problem in the salmon. In this animal the sexual cells seem to be formed at the expense of the substances of the muscles, and it was the disappearance of the muscles at the time the sexual organs began to grow which aroused Miescher's interest. But this seems to be after all of only secondary importance, inasmuch as with our present knowledge of the chemistry of living organisms it is immaterial whether the animal's own muscles furnish the material for the sexual cells or the muscles of the animal it devours. The real problem is, how it happens that at a certain stage in the development of the animal the sexual glands take away so much material from the blood. From our present knowledge we must suspect that the mechan- ism of such a process is a transformation of liquid constituents of the blood into solid constituents inside of those cells which show a rapid growth or a transformation into different compounds.

We possess a little more knowledge concerning sexual dimorphism. It has been known for a long time that it is possible to produce in plant lice (Aphis) either females exclusively, or both sexes, at desire. In bees and related forms, as a rule, only males originate from unfertil- ized eggs, and females only from fertilized eggs. It is known, more- over, that in higher vertebrates such twins as originate from the same eggs are also uniform in sex, while twins originating from different eggs may be different in sex. All that we know thus far concerning the origin of sex seems to indicate that the sex of the embryo is already determined in the unfertilized egg, or is determined very soon after the impregnation of the egg.

Sexual maturity is sooner or later followed by death. Is death determined just as automatically by the processes of development pre- ceding it, e.g. the maturation of the sexual products, as are these pro- cesses by the previous processes of development, or as is the develop- ment of the egg by the entrance of a spermatozoon? The fact that most higher animals, at least, die by bacterial infection, and that cer- tain plants, e.g. the Sequoia, which are more free from bacteria, can reach an almost fabulous age, renders the answer to this question some- what uncertain or prevents the generalization of an answer. . It is not

impossible that further experiments on the egg may aid us in solving this problem. In certain forms, e.g. the starfish, the mature egg, if not fertilized, dies rapidly, while the fertilized egg continues to live. For this egg the act of impregnation is a life-saving act. We shall now attempt to give a short sketch of the phenomena and problems of self-preservation similar to that just given of the phe- nomena of development. Among the phenomena of self-preservation are such facts as the existence of automatic mechanisms for the union of the sexual cells wherever there exist separate sexes, or the existence of automatic mechanisms for the deposition of eggs in places which furnish food for the young larvae, and so on. What do we know con- cerning the nature of these automatic mechanisms? Metaphysics has supplied us in these cases with the terms "instinct" and "will." We speak of instinct when an animal, apparently unconsciously, executes motions or actions which are necessary for the preservation of the in- dividual or the species; while we speak of will when motions are exe- cuted consciously. We call it instinct when the female fly deposits her eggs on meat on which the young larvae can feed. An analysis of the instinctive actions has yielded the result that the purposeful motions of animals frequently depend upon mechanisms which are a function of the symmetrical structure and the symmetrical distribution of irrita- bility on the surface of the body of the organisms. Symmetrical points on the surface of an animal have usually an equal irritability, i.e. if such spots are stimulated equally the same amount of motion, but in opposite directions, is produced. Points on the surface which are nearer the oral pole of the animal usually have a higher irritability than, or a different irritability from, points which are nearer the aboral pole. If lines of force, e.g.

rays of light, current curves, lines of gravi- tation, lines of diffusion, strike one side of an animal in greater density than the other side, the tension of the muscles, or contractile elements, on both sides of the organism does not remain the same, and if the animal moves, a tendency to turn to one side must result. This will continue until symmetrical points on both sides of the animal are again struck at the same angle by the lines of force. As soon as this occurs the ten- sion of the muscles, or contractile elements, on both sides of the animal becomes equal, and there is no more reason why the animal should deviate toward the right or the left ; it will therefore continue to move in the original direction. This automatic orientation in a field of force toward or away from the center of force is called a tropism. It has been possible to dissolve a number of animal instincts into tropisms. The analysis of various tropisms has shown that there exists a great variety, and often a great complexity due to the combination of several

forms of tropisms in the same individual, and to the changes of these tropisms under the influence of internal and external factors. In these lectures we shall discuss some of the elementary tropisms and their role in the animal instincts and in the preservation of the indi- vidual and the species. The will actions of animals, i.e. those motions which are executed consciously, will not be discussed here as I have already analyzed them in another book.* I will simply state here that I consider conscious- ness the function of a definite machine or mechanism, which we may call the mechanism of associative memory. Whatever the nature of this machine may be it has one essential feature in common with the phonograph, namely, that it reproduces impressions in the same chrono- logical order as that in which they were received. The mechanism of associative memory seems to be located - - in vertebrates - - in the cere- bral hemispheres. It follows from the experiments of Goltz that one of the two hemispheres is sufficient for all the phenomena of memory and consciousness. As far as the chemical or physical mechanism of memory is concerned, we have at present only a few vague data. H. Meyer and Overton have pointed out that substances which are easily soluble in fat are also, for the most part, strong anaesthetics, e.g. ether, chloro- form, etc., and that the ganglionic cells are especially rich in lipoids. It is possible that the mechanism of associative memory depends in part upon the properties and activities of the fatty constituents of the cerebral hemispheres. Another fact which may be of importance is the observation of Speck that if the partial pressure of oxygen in the air is lowered to below one third of its normal value, the fundament of mental activity, namely, memory, is almost instantly interfered with, and total loss of consciousness rapidly follows.

In those animals which possess the mechanism of associative memory, a number of the automatically regulated processes may become con- scious. Respiration is purely an automatic process, yet we may at any time become conscious of it. This has misled a number of authors to believe that such automatic processes as in ourselves may become conscious must be accompanied by consciousness in any animal in which they occur. These authors overlook the fact that the automatic mech- anisms of self-preservation must occur in every organism, while an apparatus for associative memory may be found only in a limited num- ber of organisms. Without such an apparatus, consciousness is impos- sible. The fact that a physiological process may become conscious in ourselves does not therefore prove that it is accompanied by conscious- ness in every organism.

* Loeb, Comparative Physiology of the Brain and Comparative Psychology. G. P. Put- nam's Sons, New York. TO-DAY every one who is familiar with the field of chemical biology acknowledges the fact that the chemistry of living matter is not spe- cifically different from the chemistry of the laboratory. We owe the certainty of this fact essentially to three publications, which may be mentioned briefly. The first contained the proof furnished by Lavoi- sier and La Place in 1780, that animal heat is produced by a process of slow combustion, and that for a certain amount of heat produced a certain amount of oxygen is consumed in the production of CO2. A measurement of the quantity of COs formed and the amount of heat produced gave approximately identical results in the case of a burning candle and a living guinea pig.*

A second step in this direction was taken when Woehler showed that an organic substance like urea, which is a product of metabolism, can be made artificially in the laboratory. "j" To-day so many of the compounds produced in the living body can be produced artificially that we can hardly understand that in 1828 Woehler's discovery was considered sensational. The discovery of Lavoisier and La Place left a doubt in the minds of scientists as to whether after all the dynamics of oxidations and of chemical reactions in general is the same in living matter and in inani- mate matter. The oxidation of food stuffs could indeed be imitated outside the body, but only at such temperatures as were incompatible with life; phenomena of digestion could be imitated, but only with the aid of acids too strong for life to continue. The way out of the difficulty was shown in a remarkable article by Berzelius.^ He pointed out that in addition to the forces of affinity, another force is active in

* Lavoisier et De la Place, Memoire sur la Chaleur, 1780. (Euvres de Lavoisier, Vol. 2. (Also in Ostwald's Klassiker der Naturwissenschaften, Nr. 40.) f Woehler, Ueber kunstliche Bildung des Harnstoffs. Poggendorfs Annalen, Vol. 12, p. 253, 1828. I Berzelius, Einige Ideen iiber eine bei der Bildung organischer Verbindungen in der lebenden Natur wirksame aber bishtr nicht bemerkte Kraft. Berzelius u. Woehler, Jahres- bericht, 1836. chemical reactions: this he called catalytic force. As an example he used Kirchhoff's discovery of the action of dilute acids in the hy- drolysis of starch to dextrose. In this process the acid is not consumed, hence Berzelius concluded that it did not act through its affinity, but merely by its presence or its contact. Another instance quoted by Berzelius was the decomposition of EL-Ch which had been investigated by Thenard. In acid solution this body is stable ; in alkaline solution, or in the presence of platinum, silver, or gold, or in the presence of fibrin of the blood, it is rapidly decomposed. In this decomposition apparently neither the fibrin, the gold, nor the platinum acted through the force of affinity, but catalytically. He then suggests that the spe- cific and somewhat mysterious reactions in living organisms might be due to such catalytic bodies as act only by their presence, without being consumed in the process. He quotes as an example the action of diastase in the potato. "In animals and plants there occur thousands of catalytic processes between the tissues and the liquids." The idea of Berzelius has proved fruitful, and the catalytic agencies which in his opinion are responsible for the characteristic reactions in living matter are the enzymes of modern biological chemistry. In some details, however, Berzelius's idea was erroneous. We now know that we have no right to assume that the catalytic bodies do not participate in the chemical reaction because their quantity is found unaltered at the end of the reaction. On the contrary, we shall see that it is probable that they can exercise their influence only by participating in the reaction, and by forming intermediary compounds, which are not stable. The catalyzers may be unaltered at the end of the reaction, and yet participate in it.

In addition we owe to Wilhelm Ostwald* the conception that the catalyzer does not as a rule initiate a reaction which otherwise would not occur, but only accelerates a reaction which otherwise would indeed occur, but too slowly to give noticeable results in a short time. Thus the existence of catalytic agencies, the so-called enzymes in living matter, explains the fact that chemical changes may occur very rapidly in the body at a comparatively low temperature and at a prac- tically neutral reaction. Catalyzers are used extensively in chemical factories, e.g. in the manufacture of sulphuric acid, so that it is impos- sible to see in their presence in living matter a specific difference between the chemistry of living and inanimate nature. The only difference is, perhaps, that living matter manufactures its own catalyzers. This, however, is part of that peculiarity mentioned in the introductory lec- ture, that living machines possess the peculiarity of automatically pre- serving themselves.

Reversible chemical processes are characterized by the fact that the reaction comes to a standstill before all the substances on one side of the equation are transformed into those on the other side. The reason is, that a point is reached when, in the unit of time, the change in one direction is just as great as the change in the opposite direction. When this occurs we say that chemical equilibrium has been established. Inasmuch as, according to Ostwald, enzymes do not inaugurate chem- ical reactions, but only accelerate them, it follows that the action of enzymes must also be reversible, if the process itself is reversible. It is the merit of Arthur Croft Hill to have first shown a few years ago that an enzyme, maltase, which accelerates the hydrolysis of maltose into dextrose, also accelerates the synthesis of dextrose into maltose when added to pure dextrose. It is no exaggeration to say that Hill's paper entirely changed the conceptions of the physiology of metabolism. We shall return to Hill's experiments later, and first discuss the revers- ible action of a fat-splitting enzyme, lipase.

It had been known for some time that the pancreas secretes an enzyme which digests fat in the intestinal canal. Kastle and Loeven- hart* showed that in all tissues and liquids of the body which contain fat, lipase can be found. A watery extract of pancreas contains a sub- stance in solution which is capable of hydrolizing fats, i.e. of splitting fats into fatty acid and alcohol. Kastle and Loevenhart showed, more- over, that the watery extract of any tissue which contains fat acts in a similar way. The chemical character of this catalytic substance is unknown, except that its efficiency is rapidly destroyed if it is heated in water. According to Taylor, f it does itself, at a high temperature, undergo a hydrolytic cleavage.

Kastle and Loevenhart showed that lipase not only accelerates the hydrolysis of fat, but also the synthesis of fat, when added to a mixture of fatty acid and alcohol. Their experiments were made on ethylbuty- rate. If an extract from the pancreas or liver was added to a mixture of ethylalcohol and butyric acid, ethylbutyrate was formed. This reversible action of lipase has the effect that the process of digestion of fat can only be completed if the products of digestion are removed. In the intestine this occurs through absorption.

The velocity of the hydrolysis of ethylbutyrate was found to be in proportion to the concentration of the lipase. This explains the fact that those tissues which possess most fat, as a rule, also possess most lipase.* The more lipase a cell possesses the quicker it will be able to convert the fatty acid and alcohol, which diffuse or are absorbed into it from the blood, into fat; and hence more fatty acid and alcohol must diffuse into such a cell in the same length of time from the blood than into a cell with less lipase.