STUDIES ON FERMENTATIOX. 237 



into solution. This small quantity of air so introduced into the 

 must, at the commencement of operations, plays a most indis- 

 pensable part, it being from the presence of this that the spores 

 of ferments which are spread over the surface of the grapes and 

 the woody part of the bunches derive the power of starting 

 their vital phenomena.* This air, however, especially when 

 the grapes have been stripped from the bunches, is in such 

 small proportion, and that which is in contact with the liquid 

 mass is so promptly expelled by the carbonic acid gas, which is 

 evolved as soon as a little yeast has formed, that it will readily 

 be admitted that most of the yeast is produced apart from the 

 influence of oxygen, whether free or in solution. We shall 

 revert to this fact, which is of great importance. At present 

 we are only concerned in pointing out that, from the mere 

 knowledge of the practices of certain localities, we are induced 

 to believe that the cells of yeast, after they have developed from 

 their spores, continue to live and multiply without the inter- 

 vention of oxygen, and that the alcoholic ferments have a mode 

 of life which is probably quite exceptional, since it is not 

 generally met with in other species, vegetable or animal. 



Another equally exceptional characteristic of yeast and 

 fermentation in general consists in the small proportion which 

 the yeast that forms bears to the sugar that decomposes. In 

 all other known beings the weight of nutritive matter assi- 

 milated corresponds with the weight of food used up, any 

 difference that may exist being comparatively small. The life 

 of yeast is entirely different. For a certain weight of j^east 

 formed, we may have ten times, twenty times, a hundred times 

 as much sugar, or even more decomposed, as we shall experi- 

 mentally prove by-and-bye ; that is to say, that whilst the 



* It has been remarked in practice that fermentation is facilitated by 

 leaving the grapes on the bunches. The reason of this has not yet been 

 discovered. Still we have no doubt that it may be attributed, principally, 

 to the fact that the interstices between the grapes, and the spaces which 

 the bunch leaves throughout, considerably increase the volume of air 

 placed at the service of the germs of ferment. 



