FERMENTATION. 55 



last of which, namely, 1. the presence of water, sugar, 

 and an albuminous matter in a state of actual change ; 

 2. warmth ; and 3. the admission of atmospheric air, 

 must be more particularly considered. 



ATMOSPHEEIC AIR. 



Many years ago an experiment was tried by Gay- 

 Lussac, which appeared to prove that although air was 

 essential to the promotion of fermentation, yet that 

 only so much was required as might serve to initiate 

 the process, which would then be continued and 

 ended without it. He placed grapes upon quicksilver 

 freed from all air bubbles, broke them with a metal 

 wire, let them remain in this state quietly for some 

 days, and then he saw no signs of fermentation. 

 When he afterwards introduced a little air bubble, 

 active fermentation was at once excited, and con- 

 tinued without interruption. 



This experiment and the conclusion drawn from it 

 have been interpreted in various ways. Not only 

 have some asserted that no air was necessary to the 

 development of fermentation; but exactly the op- 

 posite has been maintained, viz., that a free admission 

 of air during fermentation improves the wine. 



Dopping and Struve* thought they had ascertained 



* Erdmann's Journ. Bd. 41, s. 275. 



