VINEGAR FERMENT AND ITS CONDITIONS OF LIFE. 33 



has suffered a small diminution of extractive substances and salts, 

 which might be set down to the account of the nourishment of 

 the ferment, but that the quantity of tartaric, malic, and succiuic 

 acids has also decreased as well as that of glycerine, and of the 

 latter even nothing may be present. Hence it must be supposed 

 that the vinegar ferment also derives nourishment from these sub- 

 stances, or that its fermenting activity acts upon them as well as 

 upon the alcohol. There is finally the very important fact for 

 the practice, which has not yet been sufficiently explained, that 

 the vinegar ferment develops more rapidly upon a fluid which, 

 besides the requisite nourishing substances, contains a certain 

 quantity of acetic acid, than upon a fluid entirely destitute of it.. 

 Regarding the supply of air, it may be said that, while for mere 

 existence the vinegar ferment requires comparatively little air, 

 large quantities of it are necessary for its vigorous augmentation 

 and fermenting activity. In the practice it is aimed to accom- 

 plish this by exposing the fluid in which the ferment lives in thin 

 layers to the action of the air, and, in fact, upon this the entire 

 process of the quick method of fabrication is based. 



Besides the above-mentioned factors the temperature to which 

 the ferment is exposed takes an important part as regards its 

 development. The limits at which the augmentation of the fer- 

 ment and its vinegar-forming activity are greatest, lie between 

 H8 and 95 F. Above this limit the formation of vinegar 

 decreases rapidly and ceases entirely at 104 F. By again 

 reducing the temperature to 86 F. the ferment reassumes its 

 activity. At a temperature exceeding 104 F. the ferment suffers 

 perceptible injury ; heated to 103 F. it becomes sensibly weaker, 

 and at first augments very slowly, regaining its original vigorous 

 development only after several generations. By raising the tem- 

 perature of the fluid to 122 F. the ferment perishes. 



To low temperatures the ferment seems to be less sensitive. 

 By lowering the temperature of a fluid showing an exuberant 

 growth of ferment to 50 F. or less, the formation of vinegar 

 continues, though at a very much reduced rate. Experiments 

 especially made for the purpose have shown that by exposing 

 wine with a growth of ferment to a temperature of 14 F. so 

 that it was converted into ice, the ferment recommenced to grow 

 3 



