PURE YEAST CULTURE. 251 



according to the composition of the wort. It follows that 

 every renewal of the yeast necessitates a new acclimatisa- 

 tion, and, therefore, one of the great advantages of single 

 race yeast is lost, namely, the permanence of the race, 

 and, in consequence, the constancy of the product." In his 

 ' Handbuch der landwirthschaftlichen Gewerbe,' Berlin, 1893, 

 Lintner describes (p. 466) my system of pure yeast culture, 

 and mentions that a mixed yeast can be prepared consist- 

 ing of several pure yeasts ; he adds, however, " but a method 

 of this kind is not to be recommended, as the conditions 

 would become unnecessarily complicated." Prior, also, re- 

 cently opposed the employment of symbiotic fermentation 

 in breweries. 



The English zymotechnologists have generally inclined 

 to the view that everything depends upon the chemical 

 composition of the wort, and this was to be so regulated 

 that the fermentation would proceed as desired. When, 

 further, all possible precautions were taken to restrict the 

 development of bacteria, it was considered that everything 

 had been done that was necessary. In short, brewery yeast 

 was not regarded from a botanical point of view. If my 

 investigations have not found the same great practical ap- 

 plication in England as elsewhere, they have at least not 

 been passed over without producing some effect. An 

 opponent of my system, Mr. Lott, recently expressed him- 

 self as follows : " Hansen's investigations into the question 

 of pure yeast have emphasised, amongst others, one fact 

 of considerable importance to brewers, namely, that there 

 are a great variety of pure yeasts and that some of these 

 varieties are suitable to one process and some to another." 

 Interest, indeed, is aroused in the varieties of yeast, and 

 in the different biological problems relating to them. In 

 every course of instruction for zymotechnologists and 

 brewers, the results of investigation in this field now play 

 an important part. If the review which 4 I gave in 1892 



