ALCOHOLIC FERMENTS. 131 



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 previously, 

 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 even pointed out 

 the reason why the question could not be decided, namely, that 

 it was not then possible to determine whether he was dealing at the 

 starting-point with 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., " 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 Saccharo- 

 mycetes all the budding-fungi which showed any marked 

 power of producing alcoholic fermentation, and it is nowhere 

 clear whether his descriptions apply to true Saccharomycetes or 

 to other budding -fungi. These yeast-fungi, which in our 

 present system may belong to very different classes, were 

 further in his book regarded as stages of development of mould- 

 fungi resembling Dematium, but no evidence was given in 

 proof of this view. Whether or not there are different species 

 of these budding-fungi (Saccharomycetes, Torula, Dematium) 

 PASTEUR leaves undetermined. His treatment of the botanical 

 problems mentioned must be regarded as having essentially 

 broken down. 



The paramount reason why this work was not able to bring 

 about the reform in brewing indicated in its preface was that 

 from the position of science at that time it was impossible to 



