ALCOHOLIC FERMENTS. 115 



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 

 regarded as stages of development of mould-fungi resembling 

 Demuxtium, 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 men- 

 tioned must on the whole be regarded as having broken down 

 in the essential points. 



The reason above all others why this work was not able to 

 bring about the reform in brewing indicated in its preface was, 

 as will be clear from what has been said above that from 

 the position of science at that time, it was not possible to see 

 clearly into the relations of the different alcoholic ferments 

 during the process of fermentation. Pasteur was therefore 

 unable to get beyond the indefinite conjectures and contra- 

 dictory views of his predecessors. In his review of the micro- 

 organisms which cause diseases in beer, he speaks only of 

 bacteria; and the view that these are the only causes of 

 diseases in beer has since been repeatedly expressed by 

 Duclaux in 1883, and by other French, English, and 

 German writers. Pasteur, basing his views on these studies, 

 recommended brewers to purify their yeast ; and in order to 

 free it from bacteria, advised its cultivation in a sugar solu- 

 tion containing tartaric acid, or in wort containing a little 

 phenol (see below). 



In contradistinction to this, Hansen, in the year 1883, 

 brought forward his doctrine that some of the most dangerous 

 and most common diseases of loiv-fermentation beer were 

 caused, not by bacteria, but by certain species of Sac- 

 charomyces, and that each of the names employed by 

 Reess, namely, Saccharomyces cerevisice, Sacch. Pastorianus, 

 Sacch. ellipsoideus, represented not one but several different 

 kinds or races. He showed that varieties which until 

 then had been incorrectly grouped under the one name 



