The belief that the agents of the chemical transformation in the cell are catalysators of a colloid nature is in complete accord with other facts that have been directly ascertained. What else are the chemists' ferments but colloid catalysators? The idea that the ferments are the essential chemical agency in the cell is calculated to meet the difficulty which arises from the smallness of the cell in appreciating its chemical processes. However large we suppose the colloid ferment molecules to be, there is room for millions of them in the smallest cell.
In the same way Ostwald attributes the greatest significance to catalysis in connection with the vital processes, and seeks to explain them on his theory of energy by reference to the duration of chemical processes. In the discourse "On Catalysis" that he delivered at Hamburg in 1901 he says:
We must recognize the enzyma as catalysators that arise in the organism during the life of the cells, and by their action relieve the living being of the greater part of its duties. Not only are digestion and assimilation controlled by enzyma from first to last, but the fundamental vital action of most organisms, the production of the necessary chemical energy by combustion at the expense of the oxygen in the air, takes place with the explicit co-operation of enzyma, and would be impossible without them. Free oxygen is, as is well known, a very inert body at the temperature of the living body, and the maintenance of life would be impossible without some acceleration of its rate of reaction.
In his further observations on catalysis and metabolism he says that they are both equally subject to the physico-chemical laws of energy.
Max Verworn has given us a very searching analysis of the molecular process in the catalytic aspect of metabolism in his Biogen Hypothesis (1903), "a critical and experimental study of the processes in living matter." He simplifies the catalytic theory of the enzyma by tracing all the phenomena of life to the catalytic metabolism of one single chemical compound, the plasm, and regards its active molecules, the biogens, as the ultimate chemical factors of the vital process. While the enzyma hypothesis assumes that there are in each cell a great number of different enzyma which are all co-ordinated, and each of which only performs its little special work, the biogen hypothesis deduces all the vital phenomena from one compound, the biogenetic plasm; and thus the biogen molecules, which increase by division into parts, are the sole factors of biological catalysis. Verworn also points out the analogy between this enzymatic process of metabolism and the inorganic processes of catalysis—for instance, in the manufacture of English sulphuric acid. A small and constant quantity of nitromuriatic acid, with the aid of air and water, converts an unlimited mass of sulphuretted acid into sulphuric acid without being changed itself; the molecule of the nitromuriatic acid breaks up steadily by the giving-off of oxygen, and is then restored by the assumption of oxygen.
The manifold and changeful phenomena of life and their sudden extinction at death seem to every thoughtful man to be something so wonderful and so different from all the changes in inorganic nature that from the very beginning of biological philosophy special forces were assumed to explain it. This was particularly due to the remarkable, orderly structure of the organism and the apparent purposiveness of the vital processes. Hence, in earlier days a special organic force (archæus insitus) was assumed, controlling the individual life and pressing the "raw forces" of inorganic matter into its service. In the same way a special formative impulse was supposed to preside over the wonderful processes of development. When physiology began to win its independence, about the middle of the eighteenth century, it explained the peculiar features of organic life by a specific vital force. The idea was generally received, and Louis Dumas endeavored thoroughly to establish it at the beginning of the nineteenth century (cf. chapter iii. of the Riddle).
As the theory of a vital force, or vitalism, plays an important part in the study of the wonders of life, has undergone the most curious modifications in the course of the nineteenth century, and has been lately revived with great force, we must give a short account of it in its various forms. The phrase can be interpreted in a monistic sense, if we understand by it the sum of the forms of energy which are especially distinctive of the organism, particularly metabolism and heredity. In this we pass no opinion on their nature, and do not say that they are specifically different from the forces of inorganic nature. We might call this monistic conception "physical vitalism." However, the usual metaphysical vitalism affirms in a thoroughly dualistic sense that the vital force is a teleological and super-mechanical principle, is essentially different from the ordinary forces of nature, and of a transcendental character. The special form in which this theory of a supernatural vital force has been presented for the last twenty years is often called Neovitalism; we might call the older form, by contrast, Palavitalism.
The older idea of the vital force as a special energy could very well be accepted in the first third of the nineteenth century, and in the eighteenth, because the physiology of the time was destitute of the most important aids to the founding of a mechanical theory. There was then no such thing as the cell-theory or as physiological chemistry; ontogeny and paleontology were still in their cradles. Lamarck's theory of descent (1809) had been done to death, like his fundamental principle: "Life is only an elaborate physical phenomenon." Hence we can easily understand how physiologists acquiesced in the vitalist hypothesis up to 1833, and supposed the wonders of life to be enigmatic phenomena that escaped physical explanation.
But the position of Palavitalism changed in the second third of the nineteenth century. In 1833 appeared Johannes Müller's classical Manual of Human Physiology, in which the great biologist not only made a comparative study of the vital phenomena in man and the animals, but sought to provide a sound basis for it in all its sections by his own observations and experiments. It is true that Müller retained to the last (1858) the current idea of a vital force, as the supreme regulator of all the vital activities. However, he did not regard it as a metaphysical principle (like Haller, Kant, and their followers), but as a natural force, subject, like all others, to fixed chemical and physical laws, and subordinate to the whole. In his comprehensive study of every single vital function—the organs of sense and the nervous system, metabolism and the action of the heart, speech and reproduction—Müller endeavored above all to establish, by close observation of the facts and careful experiments, the regularity of the phenomena, and to explain their development by a comparison of the higher and lower forms. Hence Johannes Müller is wrongly described—as he has been of late—as a vitalist; he was rather the first physiologist to provide a physical foundation for the current metaphysical vitalism. He really gives an indirect proof of the reverse theory, as E. Dubois-Reymond rightly observed in his brilliant memorial speech. In the same way Schleiden (1843) cut the ground from under vitalism in botany. By his cell-theory (1838) he showed the unity of the multicellular organism to be the resultant of the functions of all the cells which compose it.