808 VISCOUS FERMENTATION. 



SECTION IX. 



LACTIC AND VISCOUS FERMENTATIONS. 



At a temperature between 86 and 104, the saccharine juices 

 of plants containing albumen or other azotised matter, undergo 

 a species of fermentation, which is different from the vinous, 

 combustible gases being evolved with carbonic acid, and a gummy 

 matter formed, having the composition of gum arabie, which 

 renders the liquid ropy and thick, and hence the application of 

 the name viscous to this fermentation. On examining the 

 liquid after effervescence ceases, it is found to contain no alco- 

 hol, but two new substances, in large quantity, namely mannite 

 and lactic acid, which together contain the elements of dried 

 grape sugar, minus 1 atom of oxygen : 



Mannite ..... C 6 H 7 O 6 

 Lactic acid. . . . C 6 H 5 O 5 



MM. Boutron and Fremy have lately observed that the 

 formation of lactic acid precedes that of the other products, 

 and that it may be produced alone, without the evolution of 

 any gas or formation of mannite. Diastase and caseum after 

 they have undergone a modification by a few days' exposure in 

 a humid state, to air, are of all organic matters containing 

 nitrogen the most efficient in determining the lactic fermenta- 

 tion. Air does not interfere by its elements, unless in trans- 

 forming the animal matter into the lactic ferment. The 

 membranes of the stomach of the dog and calf have no action, 

 when well washed with cold water and fresh, on neutral subs- 

 tances, such as sugar and, dextrin, but after being preserved for 

 some time in water, they acquire then the property to transform 

 such matters rapidly into lactic acid. These membranes some- 

 times produce another acid, differing from the lactic, of which 

 the salt of lime is insoluble in alcohol, while the lactate of lime 

 is readily soluble in that liquid. The substance of bladder after 

 being exposed humid till it begins to decompose, also excites 

 the lactic fermentation. 



