CHAPTER V.THE EMANCIPATION OF SCIENTIFIC RESEARCH FROM THE YOKE OF PHILOSOPHICAL THEORIES.
The excessive use of Hypothetical Agents in Physiological Explanations—§ 1.Vital Phenomena in Fully-constituted Organisms—Provisory Exclusion of the Morphogenic idea—The Realm of the Morphogenic Idea as the Sanctuary of Vital Force—§ 2.The Physiological Domain properly so called—Harmony and Connection of Phenomena—Directive Forces—Claude Bernard’s Work—Exclusion of Vital Force, of Final Cause, of the “Caprice” of Living Nature—Determinism—The Comparative Method—Generality of Vital Phenomena—Views of Pasteur.
The theories whose history we have just sketched in broad outline long dominated science and exercised their influence on its progress.
This domination has ceased to exist. Physiology has emancipated itself from their sway, and this, perhaps, is the most important revolution in the whole history of biology. Animism, vitalism, materialism, have ceased to exercise their tyranny on scientific research. These conceptions have passed from the laboratory to the study; from being physiological, they have become philosophical.
This result is the work of the physiologists of sixty years ago. It is also the consequence of the general march of science and of the progress of the scientific spirit, which shows a more and more marked tendencyto separate completely the domain of facts from the domain of hypotheses.
Excessive Use of Hypothetical Agents in Physiological Explanations.—It may be said that in the early part of the nineteenth century, in spite of the efforts of a few real experimenters from Harvey to Spallanzani, Hales, Laplace, Lavoisier, and Magendie, the science of the phenomena of life had not followed the progress of the other natural sciences. It remained in the fog of scholasticism. Hypotheses were mingled with facts, and imaginary agents carried out real acts, in inexpressible confusion. The soul (animism), the vital force (vitalism), and the final cause (finalism,teleology) served to explain everything.
In truth, it was also at this time that physical agents, electric and magnetic fluids, or, again, chemical affinity, played an analogous part in the science of inanimate nature. But there was at least this difference in favour of physicists and chemists, that when they had attributed some new property or aptitude to their hypothetical agents they respected what they attributed. The physiological physicians respected no law, they were subject to no restraint. Their vital force was capricious; its spontaneity made anticipation impossible; it acted arbitrarily in the healthy body; it acted more arbitrarily still in the diseased body. All the subtlety of medical genius was called into play to divine the fantastic behaviour of the spirit of disease. If we speak here of physiologists and doctors alone and do not quote biologists, it is because the latter had not yet made their appearance as authorities; their science had remained purely descriptive, and they had not yet begun to explain phenomena.
Such was the state of things during the first years of the nineteenth century. It lasted, thanks to the founders of contemporary physiology—Claude Bernard in France, and Brücke, Dubois-Reymond, Helmholtz, and Ludwig in Germany—until a separation took place between biological research and philosophical theories. This delimitation operated in physiology properly so called—i.e.in a branch of the biological domain in which as yet joint tenancy had been the rule. An important revolution fixed the respective divisions of experimental science and philosophical interpretation. It was understood that the one ends where the other begins, that the one follows the other, that one may not cross the other’s path. There is between them only one doubtful region about which there is dispute, and this uncertain frontier is constantly being shifted and science daily gains what philosophy loses.
A displacement of this kind had taken place at the time of which we speak. It was agreed, that as far as concerns the phenomena which take place ina constructed and constituted living organism, it would no longer be permissible to allow to intervene in their explanation forces or energies other than those which are brought into play in inanimate nature. Just as when explaining the working of a clock, the physicist will not invoke the volition or the art of the maker, or the design that he had in view, but only the connection of causes and effects which he has utilized; so, for the living machine, whether themost complex, such as the human body, or the most elementary, such as the cell, we may not invoke a final cause, a vital force, external to that organism and acting on it from without, but only the connections and the fluctuations of effects which are the sole actual and efficient causes. In other words Ludwig, and Claude Bernard in particular, expelled from the domain of active phenomenality the three chimeras—Vital Force, Final Cause, and the “Caprice” of Living Nature.
But the living being is not only acompletely constructed and completely constitutedorganism. It is not a finished clock. It is a clock which is making itself, a mechanism which is constructing and perpetuating itself. Nothing of the kind is known to us in inanimate nature. Physiology has found—in what is called morphogeny—its temporary limit. It is beyond this limit, it is in the study of phenomena by which the organism is constructed and perpetuated, it is in the region of the functions of generation and development, that philosophical doctrines expand and flourish. This is the present frontier of these two powers, philosophy and science. We shall presently delimit them more precisely. W. Kühne, a well-known scientist whose death is deplored, not in Germany alone, amused himself by studying the division of biological doctrines among the members of learned societies and in the world of academies. He summed up this kind of statistical inquiry by saying in 1898 at the Cambridge Congress, that physiologists were nearly all advocates of the physico-chemical doctrine of life, and that the majority of naturalists were advocates of vital force, and of the theory of final causes.
Domain of the Morphogenic Idea as the Last Sanctuary of Vital Force.—We see the reason for this. Physiology, in fact, has taken up its position in the explanation of the functional activity of the constituted organism—i.e., on a ground where intervene, as we shall show further on, no energies and no matter other than universal energies and matter. Naturalists, on the other hand, have more especially considered—and from the descriptive point of view alone, at least up to the times of Lamarck and Darwin—the functions, the generation, the development and the evolution of species. Now these functions are most refractory and inaccessible to physico-chemical explanations. So, when the time came to give an account of what they had done, the zoologists had substituted for executive agents nothing but vital force under its different names. To Aristotle it is the vital force itself which, as soon as it is introduced into the body of the child, moulds its flesh and fashions it in the human form. Contemporary naturalists, the Americans C. O. Whitman and C. Philpotts, for example, take the same line of argument. Others, such as Blumenbach and Needham, in the eighteenth century, invoked the same division under another name, that of thenisus formativus. Finally, others play with words; they talk of heredity, of adaptation, of atavism, as if these were real, active, and efficient beings; while they are only appellations, names applied to collections of facts.
This region was therefore eminently favourable to the rapid increase of hypotheses, and so they abounded. There were the theories of Buffon, of Lamarck, of Darwin, of Herbert Spencer, of E. Haeckel, of His, of Weismann, of De Vries, andof W. Roux. Each biologist of any mark had his own, and the list is endless. But here already this domain of theoretical speculation is checked on various sides by experiment. J. Loeb, a pure physiologist, has recently given his researches a direction in which zoology believes may be found the explanation of the mysterious part played by the male element in fecundation. On the other hand, the first experiment of the artificial division of the living cell (merotomy), with its light upon the part played by the nucleus in the preservation and regeneration of the living form, is also the work of a physiological experimenter. It dates back to 1852, and is due to Augustus Waller. This experiment was made on the sensitive nervous cell of the spinal ganglions and on the motor cell of the anterior cornua of the spinal cord. The effects were correctly interpreted twelve or fifteen years later. All that zoologists have done is to repeat, perhaps unconsciously, this celebrated experiment and to confirm the result.
Thus we see that the attack upon the vitalist sanctuary has commenced. But it would be a grave mistake to suppose that final cause and vital force are on the point of being dislodged from their entrenchments. Philosophical speculation has an ample field before it. Its frontiers may recede. For a long time yet there will be room for a more or less modernized vitalism.
Vitalism is even found installed in the region of physiology, although for the moment this science limits its ambition to the consideration of the completely constructed organized being, perfected in its form. The explanation of the working of this constituted machine cannot be complete until we take into account the harmony and the adjustment of its parts.
Harmony and Connection of Parts: Directive Forces.—These constituent parts are the cells. We know that the progress of anatomy has resulted in the cellular doctrine—i.e., in the two-fold affirmation that the most complicated organism is composed of microscopic elements, the cells, all similar, true stones of the living building, and that it derives its origin from a single cell, egg, or spore, the sexual cell, or cell of germination. The phenomena of life, looked at from the point of view of the formed individual, are therefore harmonized in space; just as, regarded from the point of view of the individual in formation and in the species, they are connected in time. This harmony and this connection are in the eyes of the majority of men of science the most characteristic properties of the living being. This is the domain ofvital specificity, of thedirective forcesof Claude Bernard and A. Gautier, and of thedominantsof Reinke. It is not certain, however, that this order of facts is more specific than the other. Generation and development have been considered by many physiologists, and quite recently by Le Dantec, as simple aspects or modalities of nutrition or assimilation, the common and fundamental property of every living cell.
The Work of Claude Bernard. Exclusion of Vital Force, of Vital Cause, of the “Caprice” of Living Nature.—It is not, however, a slight advance or inconsiderable advantage to have eliminated vitalistic hypotheses from almost the whole domain of present-day physiology, and to have them, as it were, thrown back into its hinterland. This is the work of the scientific men of the first half of the nineteenth century, and particularly of Claude Bernard, who has thereby won the name of the founder or lawgiver of physiology. They found in the old medical school an obstinate adversary glorying in its sterile traditions. In vain was it proved that vital force cannot be an efficient cause; that it was a creation of the brain, an insubstantial phantom introduced into the anatomical marionette and moving it by strings at the will of any one—its adepts having only to confer upon it a new kind of activity to account for the new act. All that had been shown with the utmost clearness by Bonnet of Geneva, and by many others. It had also been said that the teleological explanation is equally futile, since it assigns to the present, which exists, an inaccessible, and evidently ultimately inadequate cause, which does not yet exist. These objections were in vain.
Determinism.—And so it was not by theoretical arguments that the celebrated physiologist dealt with his adversaries, but by a kind of lesson on things. In fact he was continually showing by examples that vitalism and the theory of final causes were idle errors which led astray experimental investigation; that they had prevented the progress of research and the discovery of the truth in every case and on every point in which they had been invoked. He laid down the principle ofbiological determinism, which is nothing but the negation of the “caprice” of living nature. This postulate, so evident that there was no need to enunciate it in the physical sciences, had to be shouted from the housetops for the benefit of supporters ofvital spontaneity. It is the statement that, under determined circumstances materially identical, the same vital phenomena will be identically reproduced.
Comparative Method.—Claude Bernard completed this critical work by laying down the laws of experiment on living beings. He commended as the rational method of research thecomparative method. This should be, and is in fact, the daily instrument of all those who work in physiology. It compels the investigator in every research bearing on organized beings to institute a series of tests, such that the conditions which are unknown and impossible to know may be regarded as identical from one test to another; and when we are certain that a single condition is variable, it compels him to discover the character of the condition we are dealing with, and to learn to appreciate, and to measure its influence. It is safe to say that the errors which are daily committed in biological work have their cause in some infraction of this golden rule. In physical science the obligation to follow the comparative method is much less felt. In most cases thewitness test[3]is useless. In physiology the witness test is indispensable.
Generality of Vital Phenomena.—If we add that Claude Bernard opposed the narrow opinion, so dear to early medicine, which limited the consideration of vitality to man, and the contrary notion of the essential generality of the phenomena of life from man to the animal, and from the animal to the plant, we shall have given very briefly an idea of the kind of revolution which was accomplished about the year 1864, the date of the appearance of the celebratedl’Introduction à la médecine expérimentale.
The ideas we have just recalled seem to be as evident as they are simple. These principles appear so well founded that in a measure they form an integral part of contemporary mentality. What scientist would nowadays deliberately venture to explain some biological fact by the intervention of the evidently inadequate vital force or final cause? And who, toaccount for the apparent inconsistency of the result, would bring forward the “caprice” of living nature? And who again would openly dispute the utility of the comparative method?
What the physiologists of to-day, according to Claude Bernard, would no longer do, their predecessors would do, and not the least important of them. Longet, for example, at a full meeting of the Académie, apropos of recurrent sensibility, and Colin (of Alfort), communicating his statistical results on the temperature of two hearts, accepted more or less explicitly the indetermination of vital facts. And why confine our remarks to our predecessors? The scientists of to-day are much the same. So here again we see the reappearance of the phantom of the final cause in so-called scientific explanations. One fact is accounted for by the necessity of the self-defence of the organism; another by the necessity to a warm-blooded animal of keeping its temperature constant. Le Dantec has recently reproached zoologists for giving as an explanation of fecundation the advantage that an animal enjoys in having a double line of ancestors. We might as well say, as L. Errera has pointed out, that the inundations of the Nile occur in order to bring fertility to Egypt.
We must not therefore depreciate the marvellous work which has emancipated modern physiology from the tutelage of early theories. The witnesses of this revolution appreciated its importance. One of them remarked as follows, on the appearance ofl’Introduction à la médecine expérimentale, which contained, however, only a portion of the theory:—“Nothing more luminous, more complete, or more profound, has ever been written upon the true principles of an art sodifficult as that of experiment. This book is scarcely known because it is on a level to which few people nowadays attain. The influence it will have on medical science, on its progress, and on its very language, will be enormous. I cannot now prove my assertion, but the reading of this book will leave so strong an impression that I cannot help thinking that a new spirit will at once inspire these splendid researches.” This was said by Pasteur in 1866. That is what he thought of the work of his senior and his rival, at the moment when he himself was about to inspire those “splendid researches” with the movement of reform, the importance and the consequences of which have no equivalent in the history of science. By their discoveries and their teaching, by their examples and their principles, Claude Bernard and Pasteur have succeeded in emancipating a portion of the domain of vital facts from the direct intervention of hypothetical agents and first causes. They were compelled, however, to leave to philosophical speculation, to directing forces, to animism, to vitalism, an immense provisory field, the field which corresponds to the functions of generation and of development, to the life of the species and to its variations. Here we find them again in various disguises.