64 PASTEUR : THE HISTORY OF A MIND 



IV 



LIEBIG 



This, then, was the result of the first attempt of the vital- 

 istic theory of fermentation to range itself as an opponent 

 of the purely chemical theory. Cagniard-Latour, Helm- 

 holtz, Schwann, were forerunners, but no one listened to 

 them. The uncertainty of their experiments and argu- 

 ments accounted for this to some extent. There was 

 another and greater obstacle, namely, the general state 

 of the scientific mind of the time. Chemistry had just 

 done such beautiful things, that it believed itself, and 

 every one believed it, capable of doing still more. It 

 did its best to explain everything, down to the most 

 mysterious phenomena of life, by the simple play of 

 physical and chemical forces, and behold how, in a 

 remote corner and one little known to science, it sees 

 reappear in the form of an animate cause, those living 

 forces which it had expelled little by little from the 

 domain of physiology. That seemed to it a step back- 

 ward. "In what respect," said Liebig, apparently 

 with reason, ''does the explanation of fermentation 

 appear to you any clearer when you have introduced 

 into it a living organism, even if it is everj'^vhere in 

 it! But you see for yourself that they are not present 

 in the putrefactions. Let us admit, if you wish, 

 although it seems very extraordinary, that the meat and 

 the sugar are destroyed by different methods. But the 

 sugar can undergo diverse fermentations, very close to 

 the alcoholic fermentation, and even frequently accom- 

 panying it: the lactic fermentations, the butyric, etc. 

 Do you find in these fermentations am'thing resembling 

 the yeast? Do they not behave exactly like the macer- 

 ations of meat? Your explanation limps, and encoun- 



