io 4 THE POPULAR SCIENCE MONTHLY. 



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 per- 

 formed in the stomach and the intestine by means of soluble fer- 

 ments secreted by the organic cells, which attack alimentary sub- 

 stances, 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 mi- 

 crobes continually brought in with the food, multiplying infi- 

 nitely, 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 cellu- 

 loses 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 noth- 

 ing 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 ex- 

 treme 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 there- 

 fore 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 reac- 

 tions, 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 mi- 

 crobic 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 



