112 LOUIS PASTEUR. 



STUDIES ON WINE. 



HAVING thus solved the problem of spontaneous 

 generation, a problem which was but a parenthesis 

 forced upon his attention, Pasteur returned to fer- 

 mentation. Guided by his studies on vinegar and 

 other observations of detail, he undertook an inquiry 

 into the diseases of wine. The explanations of the 

 changes which wine was known to undergo rested 

 only on hypothesis. From the time of Chaptal, who 

 was followed by Liebig and Berzelius, all the world 

 believed wine to be a liquid in which the various 

 constituents react upon each other mutually and 

 slowly. The wine was thought to be continually 

 ' working.' When the fermentation of the grape is 

 finished, equilibrium is not quite established between 

 the diverse elements of the liquor. Time is needed 

 for them to blend together. If this reciprocal action 

 be not regular, the wine becomes bad. This was, in 

 other words, the doctrine of spontaneity. Without 

 support from carefully reasoned experiments, those 

 explanations could not satisfy Pasteur, especially at a 



