§ 1 Energy at Play in Living Beings. Common or Physical Energies. Vital Energies
Our first object will be to define and to enumerate the energies at play in living beings; to determine their more or less easy transformations from one to another, to bring to light the general laws which govern those transformations, and finally to apply them to the detailed study of phenomena. This programme may be divided into four parts.
In the physical world the specific forms of energy are not numerous. When we have mentioned mechanical, chemical, radiant (thermal and photic) energies, electrical energy, with which is blended magnetic energy, we have exhausted the catalogue of natural agents.
But is this list for ever closed? Are vital energies comprised in this list? These are the first questions which we must ask ourselves.
The iatro-mechanical school, on a priori grounds give an affirmative answer. No doubt there are in the living organism many manifestations which are pure physical manifestations of known energies, mechanical, chemical, thermal, etc. But are all the manifestations of the living being of this order? Are they all, henceforth, reducible to the categories and varieties of energy which are investigated in physics? This is the claim of the mechanical school. But the claim is rash. Our fundamental postulate affirms, in principle, that universal energy is manifested in living beings; but, as a matter of fact, there is no reason for the assertion that it does not assume particular forms, according to the circumstances peculiar to the conditions under which they are produced.
These special forms of energy manifested in the conditions suitable to living beings would swell the list drawn up by the physicists. And it would not be the first instance of an extension of this kind. The history of science records many remarkable cases. Scarcely a century has passed since we first heard of electrical energy. This discovery in the world of energy, which took place, so to speak, before our very eyes, of an agent which plays so large a part in nature, clearly leaves the door open to other surprises.
We shall therefore concede that there may be other forms of energy at work in living beings than those we already know in the physical world. This reservation would enable us to discover at once the essential characteristics by which vital phenomena are henceforth reduced to universal physics, and the purely formal differences still distinguishing them.
If there are really special energies in living beings, our monistic postulate leads us to assert that these energies are homogeneous with the others, and that they do not differ from them more than they differ among themselves. It is probable that some day they will be discovered external to living bodies, if the material conditions (which it is always possible to imagine) are realized externally to them. And if we must admit that the peculiarity of the medium is such that these forms must remain indefinitely peculiar to living beings, we may assert with every confidence that these special energies do not obey special laws. They are subject to the two fundamental principles of Robert Mayer and Carnot. They are exchanged according to fixed laws with the other physical forms of energies at present known.
To sum up, then, we must establish three categories in the forms of energy which express the phenomena of vitality.
In the first place, most of these energies are those which have already been studied and recognized in general physics. They are the same energies: chemical, thermal, mechanical, with their characteristics of mutability, their lists of equivalents, and their actual and potential stales.
In the second place, it may happen, and it probably will happen, as it happened in the last century in the case of electricity, that some new form of energy will be discovered belonging to the universal order as to the living order. This will be a conquest of general physics as well as of biology.
And finally we may rigorously and provisionally admit a last category of vital energies properly so called.
It is difficult to give much precision to the idea of vital energies properly so called.
It will be easier to measure them by means of equivalents than to indicate their nature. Besides, this is the ordinary rule in the case of physical agents. We can measure them, although we know not what they are.
Characteristics of Vital Energies.—We see why we cannot exhibit with precision, a priori, the nature of vital energies. In the first place, they are expressed by what takes place in the tissues in activity, and this cannot at present be identified with the known types of physical, chemical, and mechanical phenomena. This is a first, intrinsic reason for not being able to distinguish them readily, since what takes place is not distinguished by the phenomenal appearances to which we are accustomed.
There is a second, intrinsic reason. These vital phenomena are intermediary, as we shall see, between manifestations of known energies. They lie between a chemical phenomenon which always precedes them, and a thermal phenomenon which always follows them. They are lost sight of, as it were, between manifestations which strike our attention. Generally speaking, intermediary energies often escape us even in physics. Only the extreme manifestations are clearly seen. In the presence of the organism we are, as it were, in electric lighting works which are run by a fall of water, and at first we only see the mechanical energy of the falling water, of the turbine and dynamo at work, and the photic energy of the lamps which give the light. Electrical energy, an intermediary, which has only a transient existence, does not impose itself on our attention.
And so vital energies for this twofold reason, intrinsic and extrinsic, are not readily apparent. To reveal them, the careful analysis of the physiologists is required. They are acts, in most cases silent and invisible, which we should scarcely recognize but by their effects, after they have terminated in familiar, phenomenal forms. This is, for example, what goes on in the muscle in process of shortening, in the nerve carrying the nervous influx, in the secreting gland. And this is what constitutes the different forms of energy which we call vital properties. M. Chauveau and M. Laulanié use the phrase physiological work to distinguish them. Vital energy would be preferable. It better expresses the analogy of this special form with the other forms of universal energy; it helps us better to understand that we must henceforth consider it as exchangeable by means of equivalents with the energies of the physical world just as they are exchangeable one with another.