STUDIES IN FERMENTATION 75 



that in the fermentation of sugar, other substances 

 besides alcohol and carbon dioxide, namely glycerin 

 and succinic acid, were regularly formed in small 

 amounts, and that these substances were formed 

 at the expense of sugar. The alcoholic fermenta- 

 tion of sugar cannot be adequately represented 

 by the simple equation in which chemists were 

 accustomed to express it. It is a complex, many- 

 sided process in which sugar yields several prod- 

 ucts, among which, as Pasteur proved, is the cel- 

 lulose constituting the substance of the cell wall 

 of the yeast plant. This suggested the intimate 

 role played by the life of the yeast cell in the 

 process of fermentation. Pasteur held that this 

 process was dependent on the vital activity instead 

 of the death of the organisms found in ferment- 

 ing matter, and he sought to ascertain the role 

 of the nitrogenous matter which must be added to 

 dissolved sugar if it is to transform into alcohol. 

 The chemists held that it acted through its decom- 

 position or merely by its presence. Pasteur, on the 

 other hand, believed that it served simply as food 

 for the yeast plants which, in common with all 

 living creatures, require nitrogenous matter for 

 building up their living substance. But the ques- 

 tion was how to put the matter to the test? 



