vi FERMENT A TION. 



the alcoholic fungi, their relationship to the diseases of beer, 

 the pure cultivation of yeast and the employment of sys- 

 tematically selected species and races. The main point is the 

 reform which I succeeded in introducing into the brewing 

 industry twelve years ago, and which has since found its way 

 into the other branches of the colossal industry in which the 

 cultivation of alcoholic ferments plays an important part, 

 including distilleries, pressed yeast factories, and the wine, 

 cider and fruit-wine industries. My work appeals, however, 

 not only to those practically engaged in the fermentation 

 industries, to technologists and chemists, but also to biolo- 

 gists, and I have, therefore, given it the additional title 

 * Contributions to the Life History of Micro-Organisms.' 



This English edition is a translation of the new edition 

 of my ' Untersuchungen aus der Praxis der Garungsindustrie.' 

 Some additions have, however, been made here and there, 

 and the book thus contains also an account of my most 

 recent investigations. It consists of a series of treatises 

 which have been published at different times. Some of these 

 have been more or less remodelled, whilst others have been 

 reproduced in the same form in which they were originally 

 published ; the latter can be recognised by the dates which 

 are printed below the titles ; and where it has been necessary 

 to make any addition, this has been done in a foot-note. 



At the time when I commenced my studies on the yeast 

 fungi and their fermentations, the practice of starting new 

 hypotheses was much in vogue ; the journals contained 

 abundant discussions concerning different possibilities, but 

 a rigorous enquiry was avoided, and no account was taken 

 of what was actually known and what was mere surmise. 

 The problem in this field was, therefore, in the first place to 



