FERMENTATION. 63 



been charged with the transformation of others, whose 

 business will it be to transform them ? 



A ferment which has finished its work, replied 

 Pasteur, and which for want of aliment cannot con- 

 tinue it, becomes in its turn an accumulation, so to 

 speak, of dead organic matters. Such, for example, 

 would be an accumulation of yeast exposed to the air. 

 Leave this mass to itself in summer temperature, and 

 you will see appear in the ulterior of the mass ana- 

 erobic vibrios and the putrefactions associated with 

 their life when protected from contact with the air. At 

 the same time, on the surface of the entire mass that 

 is to say, that which finds itself in immediate contact 

 with the oxygen of the air the germs of bacteria, the 

 seeds of mould will grow, and, by fixing the oxygen, 

 determine the slow combustions which gasify the mass. 

 The ferments of ferments are simply ferments. As 

 long as the aerobic ferments of the surface have at 

 their disposal free oxygen, they will multiply and con- 

 tinue their work of destruction. The anaerobic vibrios 

 perish for want of new matter to decompose, and they 

 form, in their turn, a mass of organic matter which, by 

 and by, becomes the prey of aerobics. The portion of 

 the aerobics which has lived becomes the prey either 

 of new aerobics of different species, or of individuals 

 of their own species, so that from putrefaction to 

 putrefaction, and from combustion to combustion, the 

 organic mass with which we started finds itself reduced 



