FERMENTATION 



23 



when the air has been deprived of the germs which it ordinarily 

 holds in a state of suspension. 



"The boiled grape-must ferments when there is introduced into 

 it a very small quantity of water in which the surface of the grapes 

 of their stalks have been washed. 



"The grape-must does not ferment when there is added to it a 

 small quantity of the juice of the inside of the grape. 



" The yeast, therefore, which causes the fermentation of the grapes 

 in the vintage-tub comes from the outside and not from the inside 



FIG. 4. Tyndall's box. One side is removed to show the construction. The 

 bent tubes at the top are to permit a free circulation of air into the interior. The 

 window at the back has one corresponding in the front (removed). Through these 

 the beam of light sent through from the lamp at the side was observed. The three 

 tubes received the infusion and were then boiled in an oil bath. The pipette was 

 for filling the tubes. (Popular Science Monthly, April, 1877.) 



of the grapes. Thus it destroyed the hypothesis of MM. Trecol and 

 Fremy, who surmised that the albuminous matter transformed 

 itself into yeast on account of the vital germs which were natural 

 to it. With greater reason, therefore, there is no longer any ques- 

 tion of the theory of Liebig of the transformation of albuminoid 

 matter into ferments on account of the oxidation." 



Pasteur's work did not stop here, for he soon proved that a disease 

 that was attacking the silkworm was caused by bacteria. And from 

 this there developed the idea that disease in general is due to bacteria. 



