Life and death

by A. Dastre

§ 2. The Physiological Domain properly so called.

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 of vital specificity, of the directive forces of Claude Bernard and A. Gautier, and of the dominants of 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 of biological 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 of vital 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 the comparative 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 the witness 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 celebrated l’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, to account 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 of l’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 so difficult 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.