PUTREFACTION AND FERMENTATION 29 



in writing. He considered putrefaction to be due to the 

 "animalcules" and said that it occurred only when there 

 was a coat of organisms on the material and only when 

 they increased and multiplied. Spallanzani's experiments 

 tended to support this view since his infusions did not 

 "spoil" when boiled and sealed. Appert's practical appli- 

 cation of this idea has been mentioned. 



Thaer, in his Principles of Rational Agriculture, pub- 

 lished in the first quarter of the nineteenth century, expressed 

 the belief that the "blue milk fermentation" was probably 

 due to a kind of fungus that gets in from the air, and stated 

 that he had prevented it by treating the milk cellars and 

 vessels with sulphur fumes or with " oxygenated hydrochloric 

 acid" (hypochlorous acid) . 



In 1836 Chevreuil and Pasteur showed that putrefaction 

 did not occur in meat protected from contamination. In 

 1837 Caignard-Latour, in France, and Schwann, in Germany, 

 independently showed that alcoholic fermentation in beer 

 and wine is due to the growth of a microscopic plant, the 

 yeast, in the fermenting wort. C. J. Fuchs described the 

 organism which is commonly called the "blue milk bacillus" 

 in 1841 and conjectured that the souring of milk was prob- 

 ably bacterial in origin. It remained for Pasteur to prove 

 this in 1857. During the following six or seven years Pas- 

 teur also proved that acetic acid fermentation, as in vinegar 

 making; butyric acid fermentation (odor of rancid butter 

 and old cheese) and the ammoniacal fermentation of urea, 

 so noticeable around stables, were each due to different species 

 of bacteria. Pasteur also, during the progress of this work, 

 discovered the class of organisms which can grow in the 

 absence of free oxygen — the anaerobic bacteria. There is 

 no question that Pasteur from 1857 on did more to lay the 

 foundations of the science of bacteriology than any other 

 one man. Influenced by Pasteur's work von Hesseling, in 

 1866, stated his belief that the process of cheese ripening, like 

 the souring of milk, was associated with the growth of fungi, 

 and Martin also, in 1867, stated that cheese ripening was 

 a process which was akin to alcoholic, lactic and butyric 

 fermentations. Kette, in 1869, asserted the probability of 



