SCIENCE AND WAR 217 



does fruit-juice produce alcohol, wine turn to vin- 

 egar, milk become sour, and butter rancid ? Pas- 

 teur's interest in these problems of fermentation was 

 stimulated by one of the industries of Lille. He was 

 accustomed to visit with his students the factories of 

 that place as well as those of neighboring French 

 and Belgian cities. The father of one of his students 

 was engaged in the manufacture of alcohol from beet- 

 root sugar, and Pasteur came to be consulted when 

 difficulties arose in the manufacturing process. He 

 discovered a relationship between the development of 

 the yeast and the success or failure of the fermenta- 

 tion, the yeast globules as seen under the microscope 

 showing an alteration of form when the fermentation 

 was not proceeding satisfactorily. In 1857 Pasteur 

 on the basis of this study was able to demonstrate 

 that alcoholic fermentation, that is, the conversion 

 of sugar into alcohol, carbonic acid, and other com- 

 pounds, depends on the action of yeast, the cells of 

 which are widely disseminated in the atmosphere. 



In this year of his second great triumph Pasteur 

 was appointed director of science studies in the Ecole 

 Normale, from which he had graduated in 1847. 

 Two years later the loss of his daughter by a com- 

 municable disease typhoid fever had a great 

 effect on his sensitive and profound mind. Many of 

 his opponents, it is true, found Pasteur implacable 

 in controversy. Undoubtedly he had the courage of 

 his convictions, and his belief that, for the sake of 

 human welfare, right views his views won by tire- 

 less experiment must prevail, gained him the name 

 of a fighter. But in all the intimate relations of life 

 his essential tenderness was manifest. Like Darwin 



