FERMENTATION BY BACTERIA. 599 



often occurs in certain kinds of wine, more especially in 

 white wine, also in the saccharine juices of turnips, 

 carrots, onions, &c. ; the fluids attacked become viscous 

 and can he drawn out in threads. The fermentation is 

 best obtained artificially by using a decoction of beer 

 yeast, which is filtered and mixed with sugar, or by 

 employing starch, rice, or barley-water containing sugar ; 

 the optimum of temperature is about 30 C. Among 

 the products of fermentation is always a kind of gum, 

 which is closely related to dextrine, and has been recently 

 termed by Bechamp " viscose " ; mannite and carbonic 

 acid are also formed. Viscose is soluble in cold water, Viacoae. 

 is precipitated by alcohol, does not reduce Fehling's 

 solution, shows the same composition as starch, and 

 rotates in the same manner as soluble starch. At times, 

 and probably owing to the action of other ferments, 

 lactic acid, butyric acid, acetic acid, and hydrogen are 

 formed. Under the most favourable circumstances 100 

 parts of sugar yield 51 '1 parts of mannite, 45 '5 parts of 

 gum, and 6'2 parts of carbonic acid; hence the fer- 

 mentation can be expressed by the formula, 50 (C 6 H 12 6 ) 

 (dextrose) = 12 (C 12 H 20 10 ) (gum) +24 (C 6 H 14 6 ) (man- 

 nite) + 12 CO,, f 12 H 2 0. Schmidt-Miilheim supposes 

 that, in this fermentation of wine, there are, in fact, two 

 fermentations taking place together ; the one which pro- 

 duces mannite and carbonic acid, and the other as the 

 result of which the gum-like substance arises. Schmidt- 

 Miilheim observed the formation of the latter substance 

 alone without simultaneous production of carbonic acid 

 and mannite in the so-called tenacious milk as the result Viscous fer- 



mentation of 



of the growth of the micrococcus described on page 21b. milk. 

 This fermentation is not a fermentation of the albuminoid 

 materials of milk, but is due to splitting up the milk- 

 sugar, or it may be also cane-sugar, grape-sugar, or 

 mannite. The viscous substance formed is precipitated 

 by alcohol as a white sticky precipitate, which only swells 

 up slightly in water, much more freely in potash lye> 

 readily reduces Fehling's solution, and is stained brown 

 by iodine and iodide of potash. The optimum of tem- 

 perature for this fermentation lies between 30 and 40 C. 



