224 MICRO-OKGANISMS AND FERMENTATION. 



temperature with sterilised hopped wort in high cylindrical 

 vessels, covered up with several layers of sterilised filter-paper ; 

 after completion of primary fermentation the liquids were 

 introduced into sterilised bottles, which were kept at a lower 

 temperature. The amounts of alcohol produced (1) when the 

 primary fermentation was interrupted, (2) during the first two 

 weeks of the after-fermentation, and (3) during the next two 

 weeks, were determined. The principal fermentation was 

 broken off as soon as it was judged by the appearance of the 

 cells that the first vigorous development had come to a stop. 

 In making this comparison we did not attempt to solve the 

 question as to the absolute amount of alcohol which these 

 species are able to produce during primary and secondary 

 fermentation, our sole object being to institute a comparison 

 between the species. 



The flavour of the fermented liquid was determined after 

 the beer had gone through a secondary fermentation at 

 a lower temperature in bottles, which were first closed 

 with cotton- wool plugs and afterwards with ground-glass 

 stoppers. 



1. Fig. 71, 1 and Fig. 73, 1. 



The cells during fermentation are comparatively small, oval, 

 linked in chains ; among them there occur big round and 

 grotesque forms. 



The yeast lies rather loose in the flask ; if shaken it does 

 not distribute itself equally in the wort, but separates into clots. 



Film-formation: After a lapse of 31-32 days a very thin 

 film covers almost the whole surface of the liquid. 



The cells of the film are of about the same size as those 

 seen during the primary fermentation ; some cells very much 

 lengthened. 



The spores, if developed at a low temperature, are small, 

 full of vacuoles, and slightly granulated ; as a rule only one or 

 two in each cell. 



At 11-12C. a few spores make their appearance on the 

 seventh day; at 25C. abundant development of spores in 40 

 hours. 



When the principal fermentation was broken off, the liquid 



