INTRODUCTION. XXV 



alcohol, the former exhaling, the latter remaining in 

 the wine. By the mycoderma aceti the wine is, in its 

 turn, converted into vinegar. Of the experiments made 

 in connection with this subject one deserves especial 

 mention. It is that in which Pasteur suppressed all 

 albuminous matters, and carried on the fermentation 

 with purely crystallisable substances. He studied the 

 deterioration of vinegar, revealed its cause, and the 

 means of preventing it. He defined the part played 

 by the little eel-like organisms which sometimes swarm 

 in vinegar casks, and ended by introducing important 

 ameliorations and improvements in the manufacture of 

 vinegar. The discussion with Liebig and other minor 

 discussions of a similar nature, which M. Eadot has 

 somewhat strongly emphasized, I will not here dwell 

 upon. 



It was impossible for an inquirer like Pasteur to 

 evade the question Whence come these minute 

 organisms which are demonstrably capable of pro- 

 ducing effects on which vast industries are built and 

 on which whole populations depend for occupation 

 and sustenance ? He thus found himself face to face 

 with the question of spontaneous generation, to which 

 the researches of Pouchet had just given fresh interest. 

 Trained as Pasteur was in the experimental sciences, 

 he had an immense advantage over Pouchet, whose 



culture was derived from the sciences of observation. 

 2 



