2. What is on _à priori_ grounds demanded as a necessity, or set aside as impossible, on the strength of the axiom of the conservation of energy, must be proved _à posteriori_ by investigation. It must be shown in detail that the difference between the organic and the inorganic is only apparent. And it is here that the mechanical view of life celebrates its greatest triumph.
For a long time it seemed as though there were an absolute difference between “inorganic” and “organic” chemistry, between the chemical processes and products found in free nature, and those within the “living” body. The same elements were indeed found in both, but it seemed as if they were subject in the living body to other and higher laws than those observed in inanimate nature. Out of these elements the organism builds up, by unexplained processes, peculiar chemical individualities, highly organised and complex combinations which are never attained in inorganic nature. This seems to afford indubitable evidence of a vital force with mysterious super-chemical capacities.
But modern chemical science has succeeded in doing away with this absolute difference between the two departments of chemistry, for it has achieved, in retorts, in the laboratory, and with “natural” chemical means, what had hitherto only been accomplished by “organic” chemistry. Since Wöhler’s discovery that urea could be built up by artificial combination, more and more of the carbon-compounds which were previously regarded as specialities of the vital force have been produced by artificial syntheses. The highest synthesis, that of proteids, has not yet been discovered, but perhaps that, too, may yet be achieved.
And further: intensive observation through the microscope and in the laboratory increases the knowledge of processes which can be analysed into simple chemical processes, both in the plant and the animal body. These are astonishing in their diversity and complexity, but nevertheless they fulfil themselves according to known chemical laws, and they can be imitated apart from the living substance. The “breaking up” of the molecules of nutritive material,—that is to say, the preparation of them as building material for the body,—does not take place magically and automatically, but is associated with definitely demonstrable chemical stuffs, which produce their effect even outside of the organism. The fundamental function of living matter—“metabolism,”—that is, the constant disruption and reconstruction of its own substance, has, it seems, been brought at least nearer to a possible future explanation by the recognition of a series of phenomena of a purely chemical nature, the catalytic phenomena (the effects of ferments or “enzymes”). Ingenious hypotheses are already being constructed, if not to explain, at least to give a general formulation of these facts, which will serve as a framework and guiding clue, as a “working hypothesis” for the further progress of investigation.