82 PEEMENTATION. 



acetic acid did not produce the same effect as tar- 

 taric acid. 



These results agree entirely with those obtained 

 from the grape fermentation. It was long known that 

 fermentation is promoted by a copious supply of tar- 

 taric acid in grape juice. Fermentation is more rapid 

 in the juice of not very ripe grapes, which contain a 

 considerable quantity of free malic acid (Schwarz) 

 than in that of perfectly ripe grapes ; and wines con- 

 taining a great deal of sugar, and therefore, as a rule, 

 less free acid, ferment more slowly than those in 

 which the proportion of sugar is smaller. 



After these general observations upon ferment and 

 fermentation, we may turn our attention directly to 

 wine ferment, and the manner in which it is formed. 

 And first, we have the investigations of Bouchardat, 

 which though by no means complete, teach us, what 

 from want of knowledge in this matter I formerly left 

 undetermined, that wine, as well as beer, ferment con- 

 sists of cells, of which only the contents are active ; 

 an observation which coincides with Quevenne's.* 



The diameter of the globules of wine ferment was 

 found by Quevenne not to exceed from ?fo to T io 

 millimeter (0'039-inch). He observed that their con- 

 tents, when acted upon by hydrochloric acid, assume 

 a beautiful violet colour (this being a characteristic 

 of albuminous bodies) ; and he also remarked that the 



* Erdmann's Journ. Bd. 14, s. 346, 1838. 



