130 MICRO-ORGANISMS AND FERMENTATION. 



1876, and this work advanced in many directions our know- 

 ledge of the phenomena connected with fermentation. The 

 main portion of this book is devoted to the doctrine that 

 every fermentation and every putrefaction is brought about by 

 micro-organisms, a doctrine which he had defended with great 

 force in earlier papers. PASTEUR'S name is with justice 

 associated with this important doctrine, since it was mainly 

 through his experiments that its truth has been confirmed and 

 recognised. The idea, however, can be traced much further 

 back. LINNE and others expressed the belief that the pro- 

 cesses of fermentation and putrefaction were caused by living 

 microscopic organisms ; but proof was not forthcoming until 

 much later. It has already been mentioned that in 1835 

 MITSCHERLICH and, later, CAGNIARD-LATOUR proved that the 

 yeast of beer and wine consists of cells which reproduce them- 

 selves by budding, and that these cells bring about alcoholic 

 fermentation. Shortly afterwards SCHWANN arrived at the 

 same conclusion. In 1838 the view was expressed that 

 different fermentations were caused by different micro-organ- 

 isms ; and it was about this time that TURPIN stated that there 

 was "no decomposition of sugar, no fermentation without the 

 physiological activity of vegetation." Eeference may be made 

 to the previous exposition of this doctrine, which in its 

 historical development is so closely related to the doctrine of 

 spontaneous generation (see " Sterilisation "). 



Important discoveries never originate from a single man, 

 but really result from the work of many investigators ; it is 

 usually, however, much easier to conceive the idea of some 

 truth than to furnish sufficient proof of its correctness. Thus, 

 although the doctrine was not new, when in 1857 PASTEUR 

 commenced his experiments, some very essential connecting 

 links were wanting, as is evident from the fact that LIEBIG 

 again gave preference to STAHL'S experiments in support of the 

 chemical theory of fermentation. The victory gained by 

 PASTEUR in this dispute constitutes the foundation of his 

 great fame. 



In his " Etudes sur la biere " PASTEUR clearly and incontest- 

 ably proves the significance of micro-organisms, and he lays 

 much stress upon the marked influence which bacteria are 



