FERMENTATION. 239 



it, fermentation takes place, and, without farther assistance 

 from air, goes through all its stages. 



Nearly all the methods made use of at the present time 

 for preserving animal and vegetable substances from decom- 

 position, are founded upon preserving them from the action 

 of air, water, and heat, as I have already shown. 



At the moment when the air, or any other external agent, 

 deprives a vegetable of ever so small a portion of one of the 

 elements which enter into its composition, the body be- 

 comes imperfect, the proportions between the principles are 

 no longer what they should be, and decomposition cainnot be 

 prevented ; there will then be formed new products by the 

 union of the elements of the vegetable among themselves, 

 or by their combination with the foreign bodies which act 

 upon them. 



When a dead body is disorganized by mingling together 

 all its principles, decomposition proceeds either with greater 

 or less rapidity, because the affinity between the parts being 

 awakened, the several agents act more readily upon it. 



Whenever man wishes to appropriate to his own use the 

 product of a fermentation, it is necessary for him to inter- 

 fere by directing the progress of it. The greatest number 

 of fruits contain all the elements necessary for forming the 

 vinous fermentation; but these elements are separate in 

 them, and it is therefore necessary to mix and incorpo- 

 rate them together by the expression of the fruit, to produce 

 this fermentation. The leaves and the woody fibre of plants 

 are susceptible of putrid decomposition ; but in order to pro- 

 duce it, they must be heaped together and moistened with 

 water. 



To produce a speedy fermentation of juices, it is neces- 

 sary to collect them in a convenient quantity, and expose 

 them to a determined degree of heat : without these pre- 

 cautions there will be, to be sure, decomposition, but often 

 without any useful result. 



The vinous fermentation is the most important of any, by 

 reason of the usefulness of its products; I shall, therefore, 

 speak particularly upon it. 



The vinous fermentation takes place only when two prin- 

 ciples of very different natures act upon and decompose 

 each other : the result of this decomposition is alcohol. 

 The first of these principles is sugar ; the second is a sub- 

 stance very similar to animal gluten, which is found more or 

 less abundantly in the various kinds of grain, and in the 

 juice of some fruits. 



