PUTREFACTION AND FERMENTATION 311 



tended to support this view, since his infusions did not " spoil" 

 when boiled and sealed. Appert's practical application 

 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 behef 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 hydro- 

 chloric 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 follow^ing 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 

 Pasteur's researches furnishing a scientific basis for many 

 processes of change in the soil. In 1873, Schlosing and 

 Miintz showed that nitrification must be due to the action 

 of microorganisms, though the discovery of the particular 



