STUDIES IN FERMENTATION 65 



which he attacked involved the answer to theo- 

 retical questions. Whether we are studying the 

 souring of milk, the fermentation of sugar, the 

 maladies of beer and wine, or the diseases of ani- 

 mals and men, the thing of fundamental importance 

 to get at is the cause of the phenomenon we are 

 dealing with. We may learn much about all these 

 things by observation and the collation of facts; 

 but if we wish to get at the root of the matter we 

 must discover causes. Knowledge of the widest 

 general import frequently comes from getting at 

 the real root of particular problems. When we 

 thoroughly understand the reasons for lactic acid 

 or alcoholic fermentation our knowledge is of great 

 service in understanding fermentation in general, 

 and the demonstration of the cause of one infec- 

 tious disease opens the way to the discovery of the 

 causes of many others. If Pasteur occupied him- 

 self with particular economic problems such as how 

 to keep wines from spoiling and silkworms from 

 dying of a destructive epidemic, he solved his prob- 

 lems in such a way that by getting at the real causes 

 in these particular cases he threw a flood of light 

 upon related phenomena that has illuminated whole 

 new fields of enquiry. 



It was a combination of theoretical and practical 



