i 4 PURE CULTURES OF 



gave rise to discussions on the degeneration and transforma- 

 tion which occur in brewery yeast. A great deal was talked 

 and written about the degeneration of yeast, and the difficulties 

 met with in breweries were to a great extent attributed to 

 this cause : no experiments were undertaken, however, upon 

 which this view was based. Attention was thus diverted 

 further and further from the possibility that these misfortunes 

 might also perhaps arise from the presence of foreign species 

 which had gained admittance into the brewery. This was 

 the standpoint when I commenced my studies in this field. 



In the above account of the publications of previous 

 workers, I have only laid stress upon the most important 

 points ; several of the questions relating to this subject are 

 discussed partly in the section headed "What is the pure 

 yeast of Pasteur," p. 130, and partly in the historical account 

 commencing on p. 157. In these chapters I have also given 

 an accurate summary of the literature. Those readers who 

 are interested in the matter will also find at the end of the 

 first-named section a statement of the main points in which 

 my doctrine differs from Pasteur's. 



4. THE PRACTICAL RESULTS WHICH HAVE BEEN 

 ACHIEVED. 



When in 1883 I applied to the late Captain J. C. Jacobsen, 

 the owner of Old Carlsberg, for permission to carry out my 

 experiments on a large scale in the brewery, he had no con- 

 fidence in my scheme, as was mentioned above. One of the 

 main objections which he raised was that a pure culture of a 

 brewery yeast could not give a satisfactory after-fermentation, 

 but that for this the wild species which I had excluded would 

 probably be necessary. There are also hints in the works of 

 Reess and Pasteur which may bear this interpretation. 



Shortly before I applied to him, some of my experiments 



