STUDIES IN FERMENTATION 77 



Pasteur's position was strengthened, also, by the 

 study of other ferments. It was found that, after 

 lactic acid fermentation had ceased, the lactate of 

 lime was capable of undergoing fermentation in 

 turn if a drop of material were added which is 

 undergoing butyric fermentation. Butyric acid is 

 the acid that makes its appearance in rancid butter. 

 Upon searching for the organisms in material un- 

 dergoing butyric acid fermentation, Pasteur was 

 surprised to find active rod-like bodies which he 

 classed as vibrios and which he believed, on ac- 

 count of their activity, to belong to the animal king- 

 dom. In this Pasteur was misled by the imper- 

 fect knowledge of his day, for it is now well known 

 that many one-celled plants, and especially bacteria, 

 move about in a most lively manner. During his 

 examination of these so-called vibrios Pasteur made 

 an interesting observation that led him eventually 

 to further generalizations on the nature of fermen- 

 tation. Taking a drop of the fermenting solution, 

 he placed it on a glass slide, covered it with a thin 

 glass cover-slip, and proceeded to study it under 

 the microscope. The organisms at first active 



mentation is not a vital process in quite the sense that Pasteur 

 thought it was, although it remains true that living organisms 

 play an essential role in ordinary fermentations. They pro- 

 duce the enzymes that do the work. 



