PRODUCED BY ALCOHOLIC FERMENTS. 181 



thought that the yeast question would be solved by chemico- 

 physiological methods.* 



The chemical-physiological researches which Nageli pro- 

 moted, however, threw no light whatever on the yeast ques- 

 tion, nor concerning the degeneration and transformation 

 of the brewery yeast. My botanical investigations had, in 

 fact, to be undertaken before it was possible to attack these 

 problems in a scientific manner. In that way inquiry will 

 again be directed to these important problems, and it is not 

 improbable that Nageli will then receive credit for his views. 



After Pasteur had discontinued (1876) his studies on beer 

 and its diseases, some investigations in the same direction 

 were published by his pupils in the years following, but none 

 of these have any direct bearing on the questions to be 

 treated here. The standpoint at which the French school had 

 arrived in the year 1883 is described in Duclaux's handbook.! 

 Thus, on p. 300, Duclaux discusses the purification of brewery 

 yeast, and recommends Pasteur's method, which has been 

 already mentioned. That this method is quite unsuitable 

 for the purpose named for, as has been shown, its employ- 

 ment favours the development of the most dangerous disease 

 germs was, therefore, not then known. With reference to 

 the examination of brewery yeast, Duclaux states, on p. 471, 

 that, with the help of the microscope, it can be ascertained 

 whether the yeast is pure or not. In accordance with this it is 

 seen, on careful perusal, that when speaking of disease germs, 

 he refers only to bacteria, and not to the Saccharomycetes. 

 This view is likewise repeated on p. 618, where he treats 

 of the diseases of beer in a separate chapter. It is exactly the 

 same standpoint at which Pasteur had arrived seven years 



* Those who desire to study the details of this subject may be referred to the 

 oft-quoted ' Zeitschr. f. das ges. Brauwesen.' In the twenty-six yearly volumes of 

 this journal will, in fact, be found the records relating to the history of brewing 

 matters during that period. 



t Duclaux, * Chimie biologique,' Paris, 1883. 



