PREFACE. 



THE present book gives an account of the morphology and 

 biology of the micro-organisms of fermentation, and it thus 

 forms a complement to the text-books which treat mainly of 

 the chemical side of the subject. 



I have attempted to give a general review of all the 

 knowledge we possess in the above-mentioned field, and have 

 described the various methods of investigation which in the 

 course of time have proved of importance. 



In discussing the organisms of fermentation and their 

 relation to industry, there are two names which in a high 

 degree especially attract our attention, namely, Pasteur in 

 the older literature, and Hansen in the more recent literature 

 of our subject. Since this book is intended to give an 

 account of the present stand-point of the science, it is 

 evident that the investigations from the Carlsberg Laboratory 

 must occupy an important position. In Chapters V. and VI. 

 will be found an accurate description of Hansen's theoretical 

 investigations on the alcoholic yeasts, of his methods for the 

 pure cultivation and analysis of yeast ; likewise an account 

 of the practical employment of his pure yeast, and of the 

 results obtained with it in breweries, distilleries, and pressed 

 yeast factories, and in the preparation of wines from the grape 

 and other fruits. 



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