200 "DISEASES" OF BEER, 



the experiments appeared to have been carried out essentially 

 in the same manner. The variation occurring in the com- 

 position of the wort in the same brewery during the year 

 may in part be the cause ; but it is also conceivable that a 

 temporary modification of the condition of the cells has some- 

 thing to do with it. We are here dealing with phenomena 

 similar to those which we often find described in connection 

 with pathogenic bacteria. In the competition which occurs 

 between the brewery yeast and the disease yeasts, the power 

 which the cells possess of accommodating themselves to 

 external circumstances also gradually comes more and more 

 into play. In my theoretical studies I hope to be able to 

 give some information in connection with this question. 



Main Result. We have now followed the beer through 

 all the stages of fermentation, in its course from the ferment- 

 ing vessel to the lager cask, and finally from this to the 

 consumer. The investigations have shown that there are 

 two species of yeast, Sacch. Pastorianus III. and Sacch. 

 ellipsoideus //., which produce the disease when they are 

 present in the pitching yeast, and are, therefore, introduced 

 at the commencement of the primary fermentation. One 

 series of experiments showed that the disease can occur 

 when the disease yeast amounts to ^ T part of the pitching 

 yeast, but, on the other hand, that it can be checked by a 

 strong attenuation and a sufficiently long storage. When the 

 disease yeast is present in larger amount, it is more difficult 

 and sometimes quite impossible to ward off the disease. 



When the infection occurs at the end of the primary fer- 

 mentation, when the beer is removed to the lager cellar, it 

 is without effect. Beer which leaves the fermenting cellar 

 without having become infected, is as a rule not attacked by 

 the disease, even when it comes in contact with the two 

 disease yeasts in the lager casks or in the pipes through 

 which it passes. It must, however, be borne in mind that 

 there are a large number of other micro-organisms besides 



