STUDIES ON FERMENTATION. 195 



yeast. The cells of the " low " yeast are slightly smaller and 

 rather more OA^al, as we have already had occasion to notice, 

 and the budding processes are considerably less ramified, 

 in consequence of which there is a comparative absence of 



globular clusters which are so striking a feature in the develop- 

 ment of " high " yeast, when examined early enough. More- 

 over, if we cause our "low " yeast to age, by leaving it for a longer 

 or shorter time in the beer which it has formed, or if we 

 exhaust it in sweetened water by leaving it for whole months 

 in a volume of sweetened water considerably larger than what 

 it is capable of fermenting, and then proceed to revive it 

 and cause it to propagate in an aerated saccharine wort capable 

 of nourishing it, this yeast will resume its original aspect, 

 as sketched and described. At most we shall observe certain 

 minute differences in the size of the cells in successive growths. 

 A very remarkable industrial characteristic of this yeast is 

 the fact that it never rises to the surface, no matter at what. 

 temperature it may be working, whether between 6° C. and 

 8° C. or 15° C. and 20° C.;* in other words, it is not buoyed 

 up by the carbonic acid gas when the fermentation is at its 

 height. At the end of the fermentation, the surface of the 

 liquid and the sides of the vessel above the level of the liquid 

 are clean and not covered with the yeast, which remains 

 altogether at the bottom of the fermented liquid. Moreover, 



* [43° F. to 46° F. or 59° F. to 68' F.] 



o 2 



