and, on the other, to fight their results with medical agents, i.e., to cure the diseases. In the empirical period of medicine, which must doubtless still be greatly prolonged, physiology and therapeutics could advance separately; for as neither of them was well established, they were not called upon mutually to support each other in medical prac tice. But this cannot be so when medicine becomes scientific: it must then be founded on physiology. Since science can be established only by the comparative method, knowledge of pathological or abnormal conditions cannot be gained without previous knowledge of normal states, just as the therapeutic action of abnormal agents, or medicines, on the organism cannot be scientifically understood without first studying the physiological action of the normal agents which maintain the phenomena of life. But scientific medicine, like the other sciences, can be established only by experimental means, i.e., by direct and rigorous application of reasoning to the facts furnished us by observation and experiment. Considered in itself, the experimental method is nothing but reasoning by whose help we methodically submit our ideas to experience, the experience of facts. Reasoning is always the same, whether in the sciences that study living beings or in those concerned with inorganic bodies. But each kind of science presents different phenomena and complexities and difficulties of investigation peculiarly its own. As we shall later see, this makes the principles of experimentation incomparably harder to apply to medicine and the phenomena of living bodies than to physics and the phenomena of inorganic bodies. Reasoning will always be correct when applied to accurate notions and precise facts; but it can lead only to error when the notions or facts on which it rests were originally tainted with error or inac curacy. That is why experimentation, or the art of securing rigorous and well-defined experiments, is the practical basis and, in a way, the executive branch of the experimental method as applied to medicine. If we mean to build up the biological sciences, and to study fruitfully the complex phenomena which occur in living beings, whether in the physiological or the pathological state, we must first of all lay down principles of experimentation, and then apply them to physiology, pathology and therapeutics. Experimentation is undeniably harder in medicine than in any other science; but for that very reason, it was never so necessary, and indeed so indispensable. The more complex the science, the more essential is it, in fact, to establish a good experimental standard, so as to secure comparable facts, free from sources of error. Nothing, I believe, is to-day so important to the progress of medicine. To be worthy of the name, an experimenter must be at once theorist and practitioner. While he must completely master the art of establishing experimental facts, which are the materials of science, he must also clearly understand the scientific principles which guide his reasoning through the varied experimental study of natural phenomena. We cannot separate these two things: head and hand. An able hand, without a head to direct it, is a blind tool; the head is powerless without its executive hand. The principles of experimental medicine will be explained in this work from the triple point of view of physiology, pathology and medicine. But before going into general considerations and special descriptions of the operative procedure proper to each of these divisions, I deem it useful to give a few explanations in this introduction in relation to the theoretic and philosophic side of the method which this book, after all, treats merely on its practical side. The ideas which we shall here set forth are certainly by no means new; the experimental method and experimentation were long ago introduced into the physico-chemical sciences, which owe them all their brilliancy. At different periods, eminent men have treated questions of method in the sciences; and in our own day Monsieur Chevreul, in all his works, is explaining very important ideas on the philosophy of experimental science. We shall therefore make no claim to philosophy. Our single aim is, and has always been, to help make the well-known principles of the experimental method pervade medical science. That is why we shall here recapitulate these principles, specially pointing out the precautions to be taken in their application, because of the very special complexity of the phenomena of life. We shall consider these difficulties, first in the use of experimental reasoning, and then in the practice of experimentation. PART ONE EXPERIMENTAL REASONING CHAPTER I OBSERVATION AND EXPERIMENT ONLY within very narrow boundaries can man observe the phenomena which surround him; most of them naturally escape his senses, and mere observation is not enough. To extend his knowledge, he has had to increase the power of his organs by means of special appliances; at the same time he has equipped himself with various instruments enabling him to penetrate inside of bodies, to dissociate them and to study their hidden parts. A necessary order may thus be established among the different processes of investigation or research, whether simple or complex: the first apply to those objects easiest to examine, for which our senses suffice; the second bring within our observation, by various means, objects and phenomena which would otherwise remain unknown to us forever, because in their natural state they are beyond our range. Investigation, now simple, again equipped and perfected, is therefore destined to make us discover and note the more or less hidden phenomena which surround us. But man does not limit himself to seeing; he thinks and insists on learning the meaning of the phenomena whose existence has been revealed to him by observation. So he reasons, compares facts, puts questions to them, and by the answers which he extracts, tests one by another. This sort of control, by means of reasoning and facts, is what constitutes experiment, properly speaking; and it is the only process that we have for teaching ourselves about the nature of things outside us. In the philosophic sense, observation shows, and experiment teaches. This first distinction will serve as our starting point in examining the different definitions of observation and experiment devised by philosophers and physicians. I. VARIOUS DEFINITIONS OF OBSERVATION AND EXPERIMENT Men sometimes seem to confuse experiment with observation. Bacon appears to combine them when he says: "Observation and experiment for gathering material, induction and deduction for elaborating it: these are our only good intellectual tools." Physicians and physiologists, like most men of science, distinguish observation from experiment, but do not entirely agree in defining the two terms. 1 Zimmermann 1 expresses himself as follows: "An experiment differs from an observation in this, that knowledge gained through observation seems to appear of itself, while that which an experiment brings us is the fruit of an effort that we make, with the object of knowing whether something exists or does not exist." This definition embodies a rather generally accepted opinion. According to this definition, observation would be noting objects or phenomena, as nature usually presents them, while experiment would be noting phenomena created or defined by the experimenter. We should set up a sort of contrast, in this way, between observers and experimenters: the first being passive in the appearance of phenomena; the second, on the other hand, taking a direct and active part in producing them. Cuvier expressed the same thought in saying: "The observer listens to nature; the experimenter questions and forces her to unveil herself.” At first sight, and considering things in a general way, this dis tinction between the experimenter's activity and the observer's pas sivity seems plain and easy to establish. But as soon as we come down to experimental practice we find that, in many instances, the separation is very hard to make, and that it sometimes even involves obscurity. This comes, it seems to me, from confusing the art of investigation, which seeks and establishes facts, with the art of reasoning, which works them up logically in the search for truth. Now in investigation there may be activity, at once of the mind and of the senses, whether in making observations or in making experiments. Indeed, if we chose to admit that observation is characterized by this alone, that men of science note phenomena which nature produces spontaneously and without interference by them, still we could Vol. I, 1 1 Zimmermann, Traité sur l'expérience en médecine. Paris, 1774. p. 45. |