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 [pg 197] 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 [pg 198] 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.

The most recent of these hypotheses is that set forth by Verworn in his book “Die Biogenhypothese.”60 He assumes, as the central vehicle of the vital functions, a unified living substance, the “biogen,” nearly related to the proteids which form the fundamental substance of protoplasm and of the cell-nucleus, and in contrast to which the other substances found in the living body are in part raw materials and reserves, and in part of a derivative nature, or the results of disruptive metabolism. Very complex chemically, “biogen” is able to operate upon the circulating or reserve “nutritive” materials in a way comparable, for instance, to the action of “nitric acid in the production of English sulphuric acid.” That is to say, it is able to set up processes of disruption and of recombination, apparently by its mere presence, but, in reality, by its own continual breaking down and building up again. At the same time it has the power, [pg 199] analogous to that of polymerisation in molecules, of increasing, of “growing.”

The case is the same in regard to physical laws. They are identical in the living and the non-living. And many of the processes of life have already been analysed into a complex of simpler physical processes. The circulation of the blood is subject to the same laws of hydrostatics as are illustrated in all other fluids. Mechanical, static, and osmotic processes occur in the organism and constitute its vital phenomena. The eye is a camera obscura, an optical apparatus; the ear an acoustic instrument; the skeleton an ingenious system of levers, which obey the same laws as all other levers. E. du Bois-Reymond, in his lectures on “The Physics of Organic Metabolism” (“Physik des organischen Stoffwechsels”),61 compiles a long and detailed list of the physical factors associated and intertwined in the most diverse ways with the fundamental phenomenon of life, namely, metabolism:—the capacities and effects of solution, diffusion of liquids, capillarity, surface tension, coagulation, transfusion with filtration, the capacities and effects of gases, aero-diffusion through porous walls, the absorption of gases through solid bodies and through fluids, and so on.

Very impressive, too, are the manifold “mechanical” interpretations of intimate vital characteristics, such as the infinitely fine structure of protoplasm. For protoplasm does not fill the cell as a compact [pg 200] mass, but spreads itself out and builds itself up in the most delicate network or meshwork, of which it forms the threads and walls, enclosing innumerable vacuoles and alveoli, and BÜtschli succeeded in making a surprisingly good imitation of this “structure” by mechanical means. Drops of oil intimately mixed with potash and placed between glass plates formed a very similar emulsion-like or foam-like structure with a visible network and with enclosed alveoli.62

Rhumbler, too, succeeded in explaining by “developmental mechanics” some of the apparently extremely subtle processes at the beginning of embryonic development (the invagination of the blastula to form the gastrula); by imitating the sphere of cells which compose the blastula with elastic steel bands he deduced the invagination mechanically from the model.63

Here, too, must be mentioned Verworn's attempts to explain “the movements of the living substance.”64 “Kinesis,” the power to move, has since the time of Aristotle been regarded as one of the peculiar characteristics of life. From the gliding “amoeboid” movements of the moneron, with its mysterious power of shifting its position, spreading itself out, and spinning out long threads (“pseudopodia”), up to the contractility [pg 201] of the muscle-fibre, the same riddle reappears in many different forms. Verworn attacks it at the lowest level, and attempts to solve it by reference to the surface tension to which all fluid bodies are subject, and to the partial relaxation of this, which forces the mass to give off radiating processes or “pseudopodia.” The mechanical causes of the suspension of the surface tension are inquired into, and striking examples of pseudopod-like rays are found in the inorganic world, for instance, in a drop of oil. Thus a starting-point is discovered for mechanical interpretations at a higher level.65