SILOS, EXSILAGE AND SILAGE. 49 



ferment is capable of producing a host of distinct fer- 

 mentations, in consequence of its ability to derive the 

 carbonaceous part of its food from very different sub- 

 stances, from sugar, or lactic acid, or glycerine, or man- 

 nite, 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, in- 

 cluding all the accessory products. 



" We do not mean to imply that the ferment in ques- 

 tion is not capable of acting on some other fermentable 

 substance and giving rise to fermentation of a very dif- 

 ferent kind. 



"Moreover, it is quite erroneous to suppose that the 

 presence of a single one of the products of a fermenta- 

 tion implies the co-existence of a particular ferment. 

 If, for example, we find alcohol among the products of 

 a fermentation, or even alcohol and carbonic acid gas 

 together, this does not prove that the ferment must be 

 an alcoholic ferment, belonging to alcoholic fermentation 

 in the strict sense of the term. Nor again, does the 

 mere presence of lactic acid necessarily imply the pres- 

 ence of lactic ferment. As a matter of fact, differ- 

 ent fermentations may give rise to one, or even several, 

 identical products."* 



The products of fermentation will then vary with 

 the character of the materials fermented and the 

 specific organism that acts upon them. In accept 

 ing the physiological theory of fermentation it will 

 not be safe to assume that specific micro-organisms are 

 the sole factors involved in the process. As a pre- 

 liminary step, starch must be changed to sugar, and 

 cane sugar must be transformed into grape sugar ; that 

 is to say, the true organized ferments cannot act directly 

 on starch or cane sugar. This change is brought about 

 by zymases, the so-called soluble ferments. 



4. 



* Studies on Fermentation, pp. 276-7. 



