symptomatology. In my opinion, medicine does not end in hospitals, as is often believed, but merely begins there. In leaving the hospital, a physician, jealous of the title in its scientific sense, must go into his laboratory; and there, by experiments on animals, he will seek to account for what he has observed in his patients, whether about the action of drugs or about the origin of morbid lesions in organs or tissues. There, in a word, he will achieve true medical science. Every scientific physician should, therefore, have a physiological laboratory; and this work is especially intended to give physicians rules and principles of experimentation to guide their study of experimental medicine, that is, their analytic and experimental study of disease. The principles of experimental medicine, then, will be simply the principles of experimental analysis applied to the phenomena of life in its healthy and its morbid states.

The biological sciences to-day are no longer seeking their path. Because of their complex nature they vacillated longer than other simpler sciences in the regions of philosophy and system; but they launched at last into the experimental path where to-day they are well advanced. So they now need only one thing more, and that is means of development. Such means are laboratories and all the conditions and instruments necessary to cultivate the scientific field of biology.

To the honor of French science, it must be stated that it had the glory of decisively inaugurating the experimental method in the science of vital phenomena. Toward the end of the last century, the renewal of chemistry strongly influenced the advance of physiological science, and the work of Lavoisier and Laplace on breathing cleared a fertile path for analytic physico-chemical experimentation on the phenomena of life. My teacher, Magendie, who was led into a medical career by this same influence, devoted his life to advocating experimentation in the study of physiological phenomena. Nevertheless, application of the experimental method to animals was hindered from the first by the lack of suitable laboratories and by all sorts of difficulties which are disappearing to-day, but from which I myself often suffered in my youth. The scientific impulse, started in France, spread through Europe, and little by little the analytic experimental method entered the realm of biological science as a general method of investigation. But this method was perfected more, and it brought forth more fruit in countries where conditions

for its development were more favorable. Throughout Germany to-day there are laboratories, called physiological institutes, which are admirably endowed and organized for the experimental study of vital phenomena. They exist in Russia also, where new ones of gigantic size are being built. Scientific production is naturally in proportion to the means of cultivation which a science possesses; there is nothing astonishing, then, in the fact that Germany, where the means of cultivating the physiological sciences are most liberally installed, is distancing other countries in the quantity of its scientific production. The genius of man, of course, cannot abdicate its supremacy in science. In experimental science, however, a scientific man is the prisoner of his ideas, if he does not learn to question nature for himself, and if he does not possess suitable and necessary tools. We cannot imagine a physicist or a chemist without his laboratory. But as for the physician, we are not yet in the habit of believing that he needs a laboratory; we think that hospitals and books should suffice. That is a mistake; clinical informa tion no more suffices for physicians than knowledge of minerals suffices for chemists or physicists. Physiological physicians must experimentally analyze the phenomena of living matter, as physicists and chemists experimentally analyze the phenomena of inorganic matter. A laboratory is therefore a condition sine qua non of the development of experimental medicine, as it was for all the other physico-chemical sciences. Without it, neither experimenters nor experimental science can exist.

I shall no longer dwell on so important a subject which cannot here be sufficiently worked out; let me end by saying that one truth is well established in modern science, namely, that scientific courses can only serve to introduce and to create a taste for the sciences. By pointing out, from a professional chair, the results as well as the methods of a science, a teacher may form the minds of his hearers and make them apt in learning and choosing their own direction; but he can never make them men of science. The laboratory is the real nursery of true experimental scientists, i.e., those who create the science that others afterward popularize. Now if we want much fruit, we must first care for our nurseries of fruit trees. The evidence of this truth will necessarily bring about general and deep reform in scientific teaching. For, I repeat, it is to-day everywhere recognized that pure science germinates and develops in

laboratories, to spread out later and cover the world with useful applications. We must, therefore, first of all attend to the scientific source, since applied science necessarily proceeds from pure science.

Science and men of science are cosmopolitans, and it seems hardly important whether a scientific truth develops at any particular spot on the globe, as long as the general diffusion of science allows all men to share in it. However I cannot help praying that my country, the evident promoter and protector of scientific progress and the starting point of the brilliant era through which experimental physical science 25 is now passing, may have great, public, physiological laboratories as soon as possible, so as to make pleiads of physiologists and young experimenting physicians. Only laboratories can teach the difficulties of science to those who frequent them; they show that pure science has always been the source of all the riches acquired by man and of all his real conquests over the phenomena of nature. This is also excellent education for the young, because it makes them understand that the present, very brilliant applications of science are merely the blossoming of earlier labors, and that those who reap the benefits to-day owe a tribute of gratitude to their predecessors who painfully cultivated the tree of science, but never saw its fruits.

I cannot here treat all the conditions necessary to a good laboratory of physiology or experimental medicine. That would obviously amount to summarizing everything still to be explained in this work. I shall therefore limit myself to adding one word. I said above, that the laboratory of a physiological physician must be the most complex of all laboratories, because the experimental analyses to be made there are the most complex of all, requiring the help of all other sciences. The laboratory of a medical physiologist must be connected with a hospital so as to receive the various pathological specimens on which scientific investigation is brought to bear. It must next include healthy and diseased animals for the study of questions of normal and pathological physiology. But as vital phenomena, whether in the normal or in the pathological state, are

*In 1771 a course in experimental physiology was given by Professor A. Portal at the Collège de France; the experiments were reported by Monsieur Collomb who published them in letter form in 1771; they were republished in 1808 with a few additions in the work by Portal entitled: Mémoires sur la nature et le traitement de plusieurs maladies, avec le précis d'expériences sur les animaux vivanis. Paris, 1800-1825.

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THE STUDY OF EXPERIMENTAL MEDICINE analyzed mainly by means of tools borrowed from physico-chemical science, instruments must necessarily be somewhat liberally provided. The solution of certain scientific questions often imperatively demands costly and complicated instruments, so that we may then say that scientific questions are secondary to the question of money. However, I do not approve the luxury as to instruments to which certain physiologists have yielded. In my opinion, we should seek to simplify instruments as much as possible, not only for pecuniary, but also for scientific reasons; for we need to learn that the more complicated the instrument, the more sources of error does it create. Experimenters do not grow great by the number and complexity of instruments; it is really the other way. The great experimenters, Berzelius and Spallanzani, made great discoveries by means of simple instruments. In the course of this work, our principle, then, will be to seek, as far as possible, to simplify means of study; for instruments must be allies not sources of error because of their complications.

PART THREE

APPLICATIONS OF THE EXPERIMENTAL METHOD TO THE STUDY OF VITAL PHENOMENA

CHAPTER I

EXAMPLES OF EXPERIMENTAL PHYSIOLOGICAL INVESTIGATION

THE ideas explained in the first two parts of this introduction will be all the better understood if we can connect them with actual investigations in experimental physiology and medicine. For this reason, I have put together in the following part a certain number of examples that seem to me appropriate. As far as possible, I have quoted from myself in all these examples, for the sole reason that, in the matter of reasoning and intellectual processes, I shall be much more certain of what I describe in telling what has happened to me than in interpreting what may have taken place in the minds of others. I am not, however, so fatuous as to give these examples as models to follow; I use them only to express my ideas better and to make my thought easier to grasp.

In scientific investigations, various circumstances may serve as starting points for research; I will reduce all these varieties, however, to two chief types:

1. Where the starting point for experimental research is an observation;

2. Where the starting point for experimental research is an hypothesis or a theory.

I. WHERE THE STARTING POINT FOR EXPERIMENTAL RESEARCH IS

AN OBSERVATION

Experimental ideas are often born by chance, with the help of some casual observation. Nothing is more common; and this is really the simplest way of beginning a piece of scientific work. take a walk, so to speak, in the realm of science, and we pursue

We