As a consequence of the preceding analyses, it seems that a definition of physiology as the science of the laws or constants of normal life would not be strictly exact for two reasons: first, because the concept of normal is not a concept of existence, in itself susceptible of objective measurement; and second, because the pathological must be understood as one type of normal, as the abnormal is not what is not normal, but what constitutes another normal. This does not mean that physiology is not a science. It is genuinely so in terms of its search for constants and invariants, its metrical procedures, and its general analytical approach. But it is easy to specify how
physiology is a science in terms of its method, less easy to specify of what
, in terms of its object. Shall we call it the science of the conditions of health? In our opinion this would already be preferable to the science of the normal functions of life since we have believed we must distinguish between the normal state and health. But one difficulty persists. When we think of the object of a science we think of a stable object identical to itself. In this respect, matter and motion, governed by inertia, fulfill every requirement. But life? Isn’t it evolution, variation of forms, invention of behaviors? Isn’t its structure historical as well as histological? Physiology would then tend toward history, which is not, no matter what you do, the science of nature. It is true that we are nonetheless struck by life’s stable quality. In short, in order to define physiology, everything depends on one’s concept of health. Raphael Dubois, who is, to our knowledge, the only nineteenth century author of a work on physiology in which a not merely etymological or purely tautological definition of it is proposed, derives its meaning from the Hippocratic theory of natura medicatrix:
The role of natura medicatrix is identified with that of the normal functions of the organism which are all more or less directly conservative or defensive. Physiology is the study of nothing other than the functions of living beings, or in other words, the normal phenomena of the living proteon or bioproteon [35, 10].