ALCOHOLIC FERMENTS. 113 



when Hansen discovered the conditions regulating the for- 

 mation of spores, and upon this basis for the first time devised 

 a method for obtaining them. 



Pasteur's " Etudes sur la biere " was published in the 

 year 1876, and this work advanced in many directions our 

 knowledge 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 processes 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 the year 1836 Cagniard-Latour proved that the 

 yeast of beer and wine consists of cells which reproduce 

 themselves by budding, and that these cells bring about 

 alcoholic fermentation. Shortly afterwards Schwann arrived 

 at the same conclusion. In the year 1838 the view was 

 expressed that different fermentations were caused by different 

 micro-organisms ; and it was about this time that Turpin 

 stated that there was " no decomposition of sugar, no fer- 

 mentation without the physiological activity of vegetation." 

 I would refer the reader to the above 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 are really the result of the work of many investigators ; 

 it is, however, in general 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 



