A HISTORY OF SCIENCE 



tact with the air, 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 in- 

 troduced into it a very small quantity of water in 

 which the surface of the grapes or their stalks have 

 been washed. 



"The grape-must does not ferment when this wash- 

 ing-water has been boiled and afterwards cooled. 



"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 out- 

 side and not from the inside of the grapes. Thus is 

 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 question of the theory of Liebig 

 of the transformation of albuminoid matter into fer- 

 ments on account of the oxidation." 



FOREIGN ORGANISMS AND THE WORT OF BEER 



"The method which T have just followed," Pasteur 

 continues, " in order to show that there exists a corre- 

 lation between the diseases of beer and certain micro- 

 scopic organisms leaves no room for doubt, it seems 

 to me, in regard to the principles I am expounding. 



" Every time that the microscope reveals in the 

 leaven, and especially in the active yeast, the produc- 

 tion of organisms foreign to the alcoholic yeast prop- 

 erly so called, the flavor of the beer leaves something 



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