40 SILOS, ENSILAGE AND SILAGE. 



that fermentation was excited by " the soluble part of 

 ferment/' and he says, however, "but before it obtains 

 this power, the decanted infusion must be allowed to 

 cool in contact with the air, and to remain some time 

 exposed to its action. When introduced into a solution 

 of sugar, in this state, it produces a brisk fermentation ; 

 but without previous exposure to the air it manifests no 

 such property. The infusion absorbs oxygen during its 

 exposure to the air, and carbonic acid may be found in 

 it after a short time. Yeast produces fermentation in 

 consequence of the progressive decomposition which it 

 suffers from the action of air and water."* 



As in the experiments of Gay-Lussac, the facts are 

 correctly stated, but in explaining them the mistake is 

 made of attributing to the air, and its oxygen, the effects 

 produced by the germs of ferments floating in the air, 

 which were so minute as to escape attention. But some- 

 thing further was needed to round out his hypothesis, 

 and in 1848 Liebig published a theory of fermentation, 

 which was substantially a revival of that of Willis (1659), 

 and Stahl (1697), and a modification of his earlier views. 



It was simply that "yeast, and in general, all animal 

 and vegetable matters in a state of putrefaction, will 

 communicate to other bodies the conditions of decompo- 

 sition in which they are themselves placed ; the motion 

 which is given to their own elements by the disturbance 

 of equilibrium is also communicated to the elements of 

 the bodies which come in contact with them." f 



This theory was generally accepted by chemists as a 

 satisfactory explanation of the phenomena of fermenta- 

 tion, but in its applications it seems to have been inter- 

 preted in accordance with the earlier views of Liebig, 

 from the frequent references to oxygen as an active 



* Chemistry in its applications to Agriculture and Physiology, 184=2. N. Y. Ed., 

 p. 46. 



tAs quoted in Schutzenberger "On Fermentation," p. 40. See also article 

 Fermentation, Encycl. Brit., 9th Ed., vol. IX, p. 94. 



