ENSILAGE AND FERMENTATION. 227 



responding variations will consequently be presented in tlie residual 

 or fermented product. As in other cases involving the activity of liv- 

 ing organisms the molecular changes taking place under such different 

 conditions can not be expressed in any definite chemical formula. 



In advocating these views, Pasteur says : " Originally, when fer- 

 mentations were put among the class of decompositions by contact- 

 action, it seemed probable, and in fact was believed, that every fer- 

 mentation had its own well-defined equation, which never varied. In 

 the present day, on the contrary, it must be borne in mind that the 

 equation of a fermentation varies essentially with the conditions un- 

 der which that fermentation is accomplished, and that a statement of 

 this equation is a problem no less complicated than that in the case 

 of the nutrition of a living being. To every fermentation may be 

 assigned an equation in a general sort of way — an equation, however, 

 which, in numerous points of detail, is liable to the thousand varia- 

 tions connected with the phenomena of life. Moreover, there will be 

 as many distinct fermentations brought about by one ferment as there 

 are fermentable substances capable of supplying the carbon element of 

 the food of that same ferment, in the same way that the equation of 

 the nutrition of an animal will vary with the nature of the food which 

 it consumes. As regards fermentation producing alcohol, which may 

 be effected by several different ferments, there will be, in the case 

 of a given sugar, as many general equations as there are ferments, 

 whether they be ferment-cells properly so called, or cells of the organs 

 of living beings functioning as ferments. In the same way the equa- 

 tion of nutrition varies in the case of different animals nourished on the 

 same food, and it is from the same reason that ordinary wort produces 

 such a variety of beers when treated with the numerous alcoholic fer- 

 ments which we have described. These remarks are applicable to all 

 ferments alike :" for instance, butyric ferment is capable of producing 

 a host of distinct fermentations, in consequence of its ability to derive 

 the carbonaceous part of its food from very different substances, from 

 sugar, or lactic acid, or glycerine, or mannite, and many others. When 

 we say that every fermentation has its own peculiar ferment, it must 

 be understood that we are speaking of the fermentation considered as 

 a whole, including all the accessory products. We do not mean to 

 imply that the ferment in question is not capable of acting on some 

 other fermentable substance, and giving rise to fermentation of a very 

 different kind. Moreover, it is quite erroneous to suppose that the 

 presence of a single one of the products of a fermentation implies the 

 co-existence of a particular ferment. If, for example, we find alcohol 

 among the products of a fermentation, ©r even alcohol and carbonic- 

 acid gas together, this does not prove that the ferment must be an 

 alcoholic ferment, belonging to alcoholic fermentations, in the strict 

 sense of the term, nor again does the mere presence of lactic acid ne- 

 cessarily imply the presence of lactic ferment. As a matter of fact, 



