assimilated, the first and a considerable function which microbes perform in society.
Microbes have other equally important and useful offices. Of these is their action in digestion. Ordinary digestion is performed in the stomach and the intestine by means of soluble ferments secreted by the organic cells, which attack alimentary substances, dissociate them, and render them assimilable; and this is perceived to be a function very similar to that of microbes. The digestive passages, however, contain immense quantities of microbes continually brought in with the food, multiplying infinitely, and performing exceedingly complex offices. Even if we take up only a few of these offices, we are compelled of necessity to assume that they intervene in digestive operations, either as aids to the organic diastases or as themselves effective agents. M. Duclaux, insisting on this point, has remarked that some celluloses are capable of being attacked only by microbes, no organic juice having sufficient strength to affect them. M. Pasteur does not believe in the possibility of digestion in a medium completely deprived of microbes.
Of the chemical activity of microbes, what we know is as nothing in comparison with what it may be. Every species, every race, every variety of microbe is charged with a special function; the division of labor is carried among them to its extreme limits, so much so that in any chemical reaction each microbe takes its part in producing the process at different stages. Each variety has its duty in the work, determines a partial dissociation of the material which another species completes, and so on to the extreme simplification of organic matter, reduced to its elementary constituents, or to such conditions as to be assimilable by the plant.
These chemical actions determined by the microbe are therefore infinite and infinitely varied. Take two examples among a thousand. Starting with a single body—sugar, for example—the microbes may transform it into dextrolactic or serolactic acid or an indifferent acid, according to their own activity, the culture medium, or the associated reactions. Reducing agents in a high degree, microbes transform sulphates into sulphites, and even into sulphurets, the latter yielding, still by means of microbic reactions, sulphohydric acid. Thus, by this mechanism of successive dislocations, microbes, starting from sulphates, end by producing sulphurous water. This simple enunciation of a very special microbic process illustrates the extreme complexity of the chemical function of microbes, which are furthermore often aided in their work by solar radiation, likewise a powerful chemical agent, the action of which, though less immense than that of microbes, is similar to it. As a chemist, the sun proceeds like a microbe—a
