The History of Biological Theories

French physiologists were also influenced by current ideas, but nevertheless, led by Bernard, Bert, and Marey, they remained true to the experimental tradition charac- teristic of their country. Some of them (Bert and Marey) were to a certain extent believers in the evolutionary theory. The idea of 'general biology' an idea which has played a somewhat important part in modern times originated in France. The word 'biology' was introduced almost simultaneously (1802) by Lamarck and by Trevi- ranus to indicate a science which dealt with the general problems common to all living organisms. Treviranus' work had no lasting effect. In 1838 Comte, however, adopted Lamarck's term to indicate a science, the subject- matter of which was the interaction between the organism and its milieu.

While Darwinism, based as it was on morphology and embryology, dominated the field of speculation, this word 'biology' could not take on any very definite meaning. It was often used indiscriminately; at one time to denote ethnology, at another oecology the study of the habits of animals and plants at another to denote biology in the Comtian sense. In modern times biology has come to the front as a subject of great importance ; yet even to-day it is not quite clear what is to be understood by the term. It denotes at one time a series of general speculation con- cerning life, at another it is synonymous with general physiology, at another it means merely the study of the

cell. Nevertheless, since 1880, the term has gradually come to have a more physiological bias. There has been an attempt to connect modern general biology with the work of Comte. 1 General biological studies represent attempts to widen the horizons of zoology and of anatomy by linking these subjects up with physiology. Physiology itself has also been revived from the decay into which it had fallen. Max Verworn's General Physiology (1894) aroused the interest of all biologists. The book is interesting for many reasons, and not least because it is the first, and perhaps also the last, Darwinian physiology.

We are all familiar with the physiological institutes of the great medical schools : masses of electric wires, rheostats, multiplicators, amplifiers, kymographs, respirometers, musical instruments, finely ground lenses, resonators this physiology is certainly one of the most costly sciences to prosecute. On the theoretical side, too, it is difficult of approach. So much mathematics, physics, and chemistry are demanded as a preliminary. Verworn broke through the spell of this old tradition ; while it lasted what had been done was perfected, but no new ground was broken. Verworn directed the attention of physiologists to the unicellular organisms ; complicated apparatus and methods are useless here. All that is needed is a good microscope and a few simple instruments.

There were, however, many faults in Verworn's work. The greatest was that the author showed himself to be in favour of an ultra-conservative answer to every concrete question. His book soon lost its original reputation; it exerted very little influence on the later developments of modern physiology. Loeb was the real founder of the modern school. He was a pupil of Goltz, a Strassburg physiologist who became famous for his experiments on the functions of the various parts of the central nervous system. In this work Goltz

1 M. E. Gley, *Les Sciences biologiques et la biologic generale', Revue Scientif., consciously allied himself with the French experimental school (with Flourens), and was opposed to the German anatomical work, such as was being done by Munk, Exner, &c. Goltz showed that the structure usually found in each part of the brain is not absolutely essential for the carrying out of the normal function of that region ; these functions may be performed by a brain that is damaged and imperfect. Function is higher than structure. Loeb applied Goltz's experimental methods to the lower animals the insects, worms, and echinoderms; he was much influenced, too, by Sachs' work on the problems of plant physiology. In his early experiments he treated the animals purely as chemical aggregates, neglecting all the facts relating to structural differentiation or to systematic position. There could be no greater contrast than between this method and the Darwinian, and it led Loeb to some very far-fetched conclusions. The older view was that we must endeavour to explain animal vision by making a detailed examination of the structure of the eye ; Loeb, however, considered that the structure of the eye is a quantite negligeable. All that matters, according to him, is light and the presence of certain chemical sub- stances within the body.

Loeb afterwards settled in America, and the result of his marvellous industry was the new science of Compara- tive Physiology. In its broad outlines this new subject followed his teaching. No attention was paid to the facts of anatomy, but the organism was treated as 'a chemical machine consisting essentially of colloidal substances', a definition which mocks at belief in any deeper significance attaching to the facts of structure. Some of Loeb's theories are so far removed from any more profound view of life that we are almost tempted not to take them seriously. He asserts of memory, for example, that c it depends in part on the nature of the fatty substances in the nervous system'. He thinks it possible 'that further investigations in this direction (on artificial fertilization)

will prove quite definitely whether and in how far the death of the adult animal is determined by the nature of life itself (i.e. whether death is a chance catastrophe which may be overcome)' (J. Loeb, Vorlesungen uber die Dynamik der Lebenserscheinungen). Loeb was, however, an original and versatile experi- menter. It will be the task of the generation which is following him to revise his methods, and to take into ac- count the fact that organic structure cannot be neglected.

In America Comparative Physiology is, with Evolu- tionary Mechanics and Comparative Paychology, the most popular branch of biology. Morgan, Wilson, Jennings, Yerkes and others are among the best-known workers in these fields. Such work is only very distantly related to Darwinism, and most of these workers pay little attention to the earlier views. In modern times very great interest is being evinced in the problems of heredity and of varia- bility. These are being attacked with great enthusiasm, with the aid of modern experimental methods. They are looked upon as physiological, rather than as evolutionary problems.

When the enthusiasm for the idea of Natural Selection began to diminish it was pointed out again and again that organic adaptations cannot be completely explained by any merely mechanical principles. This argument was used to attack the whole evolutionary position ; it is, how- ever, only valid as a criticism of Darwin's explanation of expediency. It does not explain away the actual facts to which Darwin attached so much importance. There is, in organic nature, much that is expedient, and Darwin, in pointing this out, had sounded the death-knell of the older morphology. The facts connected with organic form were removed from the realm of metaphysics. Organisms were no longer looked upon as structures which were absolutely rigid and unalterable. They had, in the past, formed part of a science of philosophical morphology

which had much in common with Plato's philosophy. Darwin dragged them down from these metaphysical regions into daily life, and examined their immediate purpose in relation to the whole environment of the living organism. He was, however, to a certain degree, still under the influence of the older point of view, for it was the static relation of the parts of the body to the environment that he dealt with. He regarded all plasticity, all power of change as something foreign to the organism, as something impressed on it by the action of forces outside itself.

More profound and, ta the same time, more concrete ideas were arrived at when workers focused their atten- tion on this idea of purpose. All life was then regarded as imbued with purpose, and definite and purposeful reactions to definite stimuli were now examined, instead of the merely mechanical adaptations to such stimuli. For this reason physiology became the leading teleological science in the post-Darwinian period. This change of ideas came about gradually. Pfliiger was perhaps the first physiologist to examine the organ in relation to its purpose, from the physiological point of view. He formulated a 'law of teleological causality', ac- cording to which 'That which causes the desire in a living organism is at the same time that which leads to the satisfaction of the desire'. Food is the cause of desire in an animal; it at the same time satisfies that desire. In general, the law asserts that the organism reacts in a pur- poseful manner to the stimuli received from its environ- ment. Giddiness is a purposeful reaction which warns us not to approach too close to a precipice. The repulsion we experience when in the neighbourhood of a corpse saves us from infection, and so on. Pfliiger ascribes such reactions to the instinctive working of mechanisms which lie buried somewhere in the dim recesses of the uncon- scious mind.

Hartmann's Physiology of the Unconscious (ist edition 1869) represents an attempt at a compromise between the mechanistic and the physiological-teleological points of view. He examines the regulatory mechanisms both physiological and pathological which are exhibited by the animal body, and describes its instinctive actions. He points out that these lead us to a conception of the animal, which contrasts in many respects with the views based on the facts of anatomy, and he pleads that the principle of teleology is at least as important as the principle of causality.

Pfluger and Hartmann did not exert any influence upon evolutionary thought. After 1880 the idea was more and more often put forward that the purposefulness of life is a phenomenon sui generis, and that it cannot be explained as the result of a summation of chance effects. This was the view ex- pressed in 1 88 1 by Montgomery, an American physician who began to publish works dealing with the philosophical aspects of biology. The idea he developed was that the organism is quite different in kind from any inorganic substance; it does not represent an aggregate not even a cell, tissue, or organ aggregate but it is a unit which exerts definite control over the actions and reactions between itself and its environment.

According to Montgomery, it consists of a chemical substance which is destroyed by the action of the external world, which is renewed by its own activity, and which, by a process of development, forms organs for itself, in order to make its functional relationship with its environ- ment a many-sided one. Virchow's pupil Rindfleisch, who succeeded him as pro- fessor at Wiirzburg, advised 'due reticence in regard to the undiscoverable' ; he laid great stress upon the specificity of living substance, and opposed Haeckel's views. The term Neovitalism is found for the first time in Rind- fleisch's work (G. E. Rindfleisch, Artzlicbe Philosopkie,

In 1889 the physiologist Bunge declared that he could not accept the mechanistic view, and pointed out how important is vital activity. Rindfleisch and Bunge suc- ceeded in interesting the public in their ideas, which were found to be stimulating, if nothing more. After 1890 the teleologists increased rapidly in number. In that year C. Wolff published his attack on the theory of Natural Selection. He affirmed that the fitness of an organism for the life it is destined to lead cannot be ex- plained; this must be accepted as a fact, an axiom. In 1891 Kerner von Marilaun, in his beautifully arranged book Plant Life, declared himself a vitalist. In 1899 Cossmann published a study in scientific methodology, in which he examines the relationship between causality and teleology; he declares the latter to be 'an unavoidable maxim for the critical judgement of biological phenomena'. * Since 1899 Reinke the botanist has come into the field in defence of teleological ideas, and has succeeded in awaken- ing considerable interest in his views. 2 He declares that Darwin's idea, that the fitness of organism to-day is to be traced back to a lesser fitness in the past, is exploded. He regards the ultimate relationship of the organism to its environment as a fact which must be accepted not explained. In order to make the difference between the teleological idea and the conception of a 'blind chance causation' comprehensible he postulates that there are two categories of forces at work within the organism; the 'energies' identical with those forces known from chemistry and physics, and the 'non-energies', which he says may be 'systematic', 'dominating', or 'psychic'.

The systematic forces depend upon the structure of the organism. The way in which a watch goes depends upon the structure of its works ; in the same manner thought depends upon the specific structure of the brain. Under 'dominant' forces Reinke includes all the 'self-formative' 1 P. N. Cossmann, Elemente der empiriscben Teleologie, Stuttgart, 1 899. Butschli, in the book to which we have already referred, mentions other vitalists, and further details are to be found in Driesch's Der Vitalismus als Gescbicbu und als Lebre, Leipzig, 1905. See also K. Braeunig, Mecbanismus und Fitalismus in der Biologic des i^ ten JabrbundertSy Leipzig, 1907.

forces of the organism those which have produced the organism from the egg. Such forces only exist in the organic world. They represent all that is really harmonious in that world ; they control the development of specific structures, such as the eye, the ear, the brain, out of the plastic material of the embryo ; they harmonize the various types of physical and chemical energy within the body, and produce a dominating control. Thus the way is pre- pared for those highest forces the psychical, which are only possessed by man and the highest animals.

In a very able treatise Lawrence Henderson goes back definitely to the pre-Darwinian conception of the purpose- ful in the universe. He assumes that the present environ- ment represents that best fitted to the life of the organism, because it is subject to laws which are advantageous to that life. The heaviest elements, for example, which are the least important for living organisms, are concentrated in the interior of the earth, while the lighter ones, out of which the living body is formed, are found at or near the earth's surface. The properties of water so dis- tinctive among liquids fit it in a quite peculiar way for the part it plays in the living body. The properties of carbon dioxide are also adapted in a remarkable manner to the needs of living organisms. The properties of the elements are no chance properties. Carbon, hydrogen, and oxygen are all endowed with special characteristics which make them particularly suitable to form the basis of organic compounds. Henderson reminds his readers that his point of view is akin to that of the Naturpbilo- sophen of the Deistic epoch.

Ideas are like men. They come into the world, but no one knows whence they came ; they grow and flourish, and for a time cherish the illusion of eternal life, and then they depart into that land 'from whose bourne no traveller returns'. This was the fate of Aristotelian science, of the ambitious science of the eighteenth century, of Cuvier's ideas, of naturalism ; this fate is now rapidly overtaking Darwinism. Many still hold that Darwin was right, and proudly point out that no one has yet given any better explanation of the facts of animal history. This is true. But Darwinism is not being replaced by a better view; it is simply being abandoned. Not one of those who had become convinced Darwinists afterwards recanted neither Darwin nor Huxley nor Spencer. But they grew old, they vanished from the world, and were replaced by new investigators, who had not experienced the vital glow aroused by the original Darwinism. They no longer under- stood its essential spirit; they have other tastes, other sympathies and antipathies, other experiences. In all this they differ from the originators of the theory. They no longer live in the theory, it is no part of them they regard it as something extraneous.

Science lives in a new setting. There are no longer any great rhetorical upholders of naturalism. There is no need any longer to emphasize the accuracy of natural science. We no longer live in revolutionary times; the words, 'liberty, equality, fraternity', have lost their pristine attraction. Famous names disappear from the field of action. Darwin is dead; and in that peaceful home to which philosophers from the whole world came as pilgrims a girls' boarding school was established. Huxley followed his friend, and his witty and sparkling essays are read less and less. Spencer is dead, and his philosophy is drowned in a flood of new systems. New names come into prominence, and a revision of values is in progress. To-day no one would speak as scornfully of Goethe as did du Bois- Reymond, that triumphant exemplar of the exact scientist. On the contrary, the reputation of Goethe, both as a biologist and a physicist, grows while that of du Bois- Reymond is constantly waning. Robert Mayer wins ever greater renown, while von Helmholtz, that pattern scientist, is quietly ignored. Naturalism is no longer banned ; it is even threatening Darwinism. The biologists have changed

their methods. The prominent biologists of to-day do not produce works on comparative anatomy, on de- scriptive embryology, or on geographical distribution, subjects which were all of such pre-eminent importance in the period of classical Darwinism. Youthful scientists no longer grow intoxicated with the direct enjoyment of Darwin's monumental works. They only know a scho- lastic Darwinism which has been robbed of all its freshness and vitality ; they no longer look at Darwin and Spencer with their own eyes, but through the eyes of Driesch and Roux, of Weismann and Sachs, of Nageli, Haeckel, or Huxley. Darwinism, that bugbear of the reactionary, no longer exists, Fuit Ilium!

The first modern criticism of Darwinism a very radical one due to Wolff appeared in 1890, and since that date the anti-Darwinian movement has grown continually. This was not realized at first it was thought that only minor matters were at stake, and people were guilty of extraordinary inconsistencies. It was felt that here was a new philosophy, and men endeavoured to grasp it, but their minds were still too full of the older ways of thinking. Ernst Mach, a physicist, revived the pre-Darwinian con- ception of motive as the logical cause of action. This was opposed to the evolutionary theory, in which the search for motives had been abandoned and had been replaced by the search for causes. Mach was absolutely unconscious of this antagonism, however, and held himself to be a perfectly orthodox and enthusiastic evolutionist. Ostwald spoke against materialism ; further, he was bold enough to plead for the revival of naturalism. But his naturalism was a tune played on one string only, 'energetik', and it enabled him to introduce Darwinian concepts even into chemistry.

Yves Delage began to feel that biological science was facing a time of crisis. He was sorry that France was watching this general spiritual ferment so unmoved, and endeavoured to arouse the interest of his compatriots. Believing that French scientists were not sufficiently in- terested in theoretical work he collected all the biological hypotheses which had gained a hearing, and published them in a great tome. But he did not produce the desired effect, for he was still immersed in Darwinian speculation and had not perceived the true nature of the controversy. Studies of systematic biology, of anatomy, of embryology, even of the cell theory, become old-fashioned ; new sub- jects hold the field. Just now it is physiology, experimental morphology, and heredity ; their problems, methods, and inferences attract our attention, and accustom us to a new series of facts and a new logic. There is in all this no direct attack on Darwinism, but young scientists have their interests directed into other channels, and look upon the earlier work as old-fashioned and inexact. Many think they see a new dawn on the horizon ; they write popular articles, in which they uphold teleology and vitalism, and attack Natural Selection, materialism, Darwinism, Haeckel, and Weismann.

Darwinism is called 'mere descriptive science'; even those corner-stones of Darwinism scientific zoology and botany are held to be out of date to-day sciences which, in the 'seventies, dominated the world. To-day we all study general biology. In fifty years' time what new solu- tion of these problems will thrill mankind ? And where shall we find a still more general name for the biological science of that era ? We can find traces of this decay of positivist science, as this was understood in the 'seventies, in biology itself. In every department of human activity a definite conviction is of the utmost value. It carries us unharmed through the chances of the day, for we are led on to certainty. Until recently there was such a conviction in biology. There were doubters, it is true ; there was no unanimity of opinion about the value of the theory of Natural Selection ; there was uncertainty about the value of certain facts and theories. But all these minor differences were as nothing before the strength of the conviction that the Darwinian theory, and all that modern science which is based on facts, were wonderful edifices built on sure and lasting

foundations. The methods of exact science led men on eagerly to pursue new facts; so arose the fashion of announcing 'sensational discoveries' discoveries which fly for a day from lip to lip, as great and epoch-making achieve- ments, to be completely forgotten to-morrow. We have experienced a whole series of these in modern times: pithecanthropus ; the chemical theories of instinct and of artificial fertilization ; the idea that ants are mere machines ; the proof that human blood is chemically akin to the blood of the monkey; cell physiology; the neuron theory; muta- tions; chromosomes; centrosomes; the theory of im- mortality, and so on. The sensational way in which scientists acclaim these facts, hypotheses, and theories, only to aban- don them again as quickly, must bring science into disrepute.

Finally, Darwinism was completely rejected. In 1893 Driesch ventured to write that 'to examine the preten- sions of that discredited theory known as the Darwinian theory would be an insult to the reader'. At that time no one paid any attention to Driesch. But he continued to develop his theory until it could no longer be ignored. We may therefore sum up the modern position in Driesch's words: 'For those with insight Darwinism has been dead for a long time. The last pronouncements in its favour were little more than funeral odes inspired by the text De mortuis nibil nisi bene ; they contained a complete admission of the inadequacy of the defence' (H. Driesch, 'Kritisches und Polemisches', BioL Zentralbl., 1902, p. 182).

Darwinism as a tyrannic doctrine, which imperiously en- chains the minds of men, is dead. But it will continue to live as a great intellectual system worked out by men with great minds and of high ideals. In the future it will be included among the greatest of the ideas which form the legacy of the past ; on it investigators of the future will train their intellectual talents. SCIENTIFIC activity to-day is based on the assump- tion that, if we increase the sum of man's inherited knowledge and pass it on to posterity, we are working for the general good. We hope by our science to widen the historical horizon. In the popular view real history history and historical writing being regarded as identical is the history heard in lecture-rooms, published in monographs, and treasured in libraries and museums. According to this view, there is very little value in the study of the history of a scientific problem, for exact science assimilates the past, so that the present includes the past.

This depreciation of the history of science began when modern scientific philosophy captured the imagination of the world. In the middle of last century, when the positivist idea of the progress of mankind was beginning to creep into science, into philosophy, and into politics, the history of science was a very popular theme. In France histories of zoology were published by Cuvier (1830-2), by de Blainville(i84S), and by Geoffroy St. Hilaire (1854) ; a history of botany by Adanson (1864), and a very com- prehensive history of palaeontology by d'Archiac (1864). In Germany, as the result of his study of comparative anatomy, Schmidt published a history of science in 1855. Inspired by Schelling and Cuvier, Spix started a history of systematic zoology (1811), while Sprengel (1817-18), and Meyer (1854), produced histories of botany. Carus' history of zoology (1872) also belongs to this period.

Even non-biologists like Comte and Buckle turned their attention to the history of science. Whewell's well-known History of the Inductive Sciences was the most famous of all these works on the historical aspects of the biological sciences. Though its contents leave much to be desired, although its survey of the various branches of biology is very unequal in value, yet it has this great merit its philosophy is original. It begins with the assumption that there is progress in human affairs, and sets out to prove that in the history of science we can descry a continual progress towards ever-higher aims. The proof of this which he proceeds to set forth in great detail is that one science, Botany, proceeds along a direct and undisturbed road to its appointed end, while other branches of biological know- ledge also advance, but less directly, making many false steps and many mistakes.