76 FERMENTATION. 



necessary to excite fermentation, a larger quantity is 

 needed in order to ensure the formation of ferment. 

 Schmidt observed that a solution of grape sugar, 

 under the influence of a solution of emulsin, which 

 had been filtered, began to ferment at the end of 

 four hours, and at the end of eight hours the fer- 

 mentation was very perceptible, whilst cells could not 

 be observed till the expiration of 36 to 48 hours.* 

 But there are here two points which must be kept 

 distinct from one another. Fermentation may exist 

 prior to the presence of ferment ; and it may be set up 

 in consequence of the addition of ferment. Fermen- 

 tation may therefore exist before the formation and 

 during the decomposition of ferment. 



Schmidt's experiments, and those which are recorded 

 (p. 68), teach us the first fact; the latter we learn 

 from seeing fermentation brought about in a solution 

 of sugar, by the addition of ferment. 



What, then, will take place in freshly pressed grape 

 juice ? We may assume, without hesitation, the two 

 aforementioned points ; fermentation begins in conse- 

 quence of the change induced in vegetable gluten or al- 

 bumen, by means of a little oxygen, and hardly has it be- 

 gun before the formation of ferment commences, and fer- 

 mentation is maintained by means of its decomposition. 



Wagner denies altogether the accuracy of the 

 results obtained by Dopping, Striive, and Schmidt,t 



* Ann. der Ch. und Pharm. Bd. 61, s. 168. 

 t Journ. fur Prakt, Chemie, Bd. 45, s. 241. 



