114 MICRO-ORGANISMS AND FERMENTATION. 



connecting links were wanting, as is evident from the fact 

 that Liebig again gave preference to StahVs 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 the micro-organisms, and he 

 lays much stress upon the marked influence which bacteria 

 are capable of exercising upon fermentation and on the 

 character of the resulting beer. He also treats of the budding- 

 fungi ; and in the case of some imperfectly described members 

 of this group, he intimates, as Bail and others had done pre- 

 viously, that they affect the character of the products of 

 fermentation in various ways. In this Pasteur is merely 

 repeating the indistinct views of previous investigators, and 

 his suggestions take two opposite directions. This is distinctly 

 seen in his observations on the so-called caseous yeast and the 

 aerobic yeast. It is possible that in this case he may have 

 been dealing with distinct kinds of yeast, but it is also 

 possible that they were merely forms of ordinary brewers' 

 yeast modified by some treatment to which they had been 

 subjected. It must not, however, be overlooked that Pasteur 

 was clear as to his position, and even pointed out the reason 

 why the question could not be decided, namely, that it was 

 not then possible to determine ivhether at the starting point 

 he was dealing with only one or with several species. An 

 accurate method for the pure cultivation of the different 

 kinds of yeast had not then been discovered (compare 

 Chapter I., 7. Preparation of the pure culture). A true 

 orientation in the world of micro-organisms is consequently 

 not found in this work, and it is not possible in any 

 part of Pasteur's statements to find such characteristics for 

 the budding-fungi on which a scheme of analysis could be 

 based. Pasteur classed with the Saccharomycetes all the 

 budding-fungi which showed any marked power of producing 

 alcoholic fermentation, and it is nowhere clear whether his 



