Expey^iment Station Report. 35 



develop rapidly in the presence of air, but their function as 

 ferments is impaired by this ready supply of oxygen. 



Jn the absence of air, as in an atmosphere of carbonic 

 acid, they take their supply of oxygen from organic sub- 

 stances, like sugar, and their function as ferments is in- 

 creased. 



When the life of the bacteria, or other organized ferments, 

 is destroyed, the process of fermentation, or putrefaction, 

 ceases ; and this takes place, — according to the observa- 

 tions made in the course of the controversy in regard to 

 spontaneous generation, — at a temperature of from 122° to 

 140°, and if the germs that produce the bacteria are then 

 excluded, the process of fermentation, or of putrefaction, 

 cannot again take place. 



The canned articles of food, which are now so common in 

 the markets, furnish an illustration of the application of this 

 principle. In their preparation heat is applied, which kills 

 the bacteria, — the active agents of fermentation, — and 

 they are then sealed in air-tight cans to prevent the access 

 of a fresh supply of germs from the atmosphere. 



That the germs which produce the bacteria of fermenta- 

 tion and putrefaction are abundantly distributed in the air, 

 has been conclusively proved by the experiments of Pasteur 

 and Tyndall, and the supposed cases of spontaneous fermen- 

 tation or putrefaction are readily explained by the seeding of 

 the fermenting substances with the germs derived from the 

 atmosphere. 



* The various and conflicting reports that are made in regard 

 to the quality of ensilage, including the degree of acidity, 

 its influence upon the quality of milk, and its general feed- 

 ing value, can only be explained by diffierences in the quality 

 and maturity of the crops from which it is made, together 

 with the different methods of securing it, all of which must 

 have an influence on the process of nutrition in the bacteria, 

 and therefore produce variations in the results of fermenta- 

 tion. 



The molecular changes taking place under such different 

 conditions cannot be expressed in any definite chemical for- 

 mula. As fermentation is strictly a physiological process, 

 the fermented product may be looked upon as the residuum 



