146 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



their mode of action being largely the same in all. Water is always essen- 

 tial to the processes of fermentation, and the result is acquired by a more 

 or less simple splitting up of the organic molecule accompanied by hy- 

 dration. The nature of this splitting up is governed by the nature of 

 the body which is subjected to fermentation, and may be explained in 

 most cases by chemical processes in which the intervention of a living 

 organism does not appear. Ferments have been classified as follows in 

 the character of the change which they produce (Hoppe-Seyler) : — 



CHANGE OF ANHYDRIDES INTO HYDRATES. 

 A. Ferments that Act like Dilute Mineral Acids at a High Temperature. 



a. The conversion of starch into sugar, or glycogen into dextrin 

 and grape-sugar, as by the action of ptyalin, the amylolytic ferment of 

 the pancreatic or intestinal juices, diastase, or the liver-ferment. Thus : — 



4(C 6 H 10 O 5 )+3H 2 O = C 6 H 10 O 5 +3(C 6 H 12 O 6 ). 

 Glycogen. Grape-Sugar. 



or, in the case of starch : — 



C 2 4H 4 „O 20 +3 H 2 = O,H 10 O, + 3 C 6 H 12 6 . 

 Starch. Water. Dextrin. Glucose. 



b. The conversion of cane- into grape-sugar, as by the inversive 

 ferment : — 



C 12 H 22 11 + H 2 = C 6 H 12 6 -fC 6 H 12 6 . 

 Cane-Sugar. Grape-Sugar. Fruit-Sugar. 



This reaction also gradually occurs through the action of water at 

 100° C, while starch requires a temperature of 170°, the resulting sugar 

 at the same time undergoing decomposition. 



B. Ferments that Act like Caustic Alkalies at a High Temperature— 

 Fermentative Saponification. 



a. Splitting up of fats into glycerin and fatty acids, as by the action 

 of the ferment of the pancreatic juice. 



b. Splitting up of amydo compounds by hydration through decom- 

 position products, as 



C0N 2 H 4 + 2H 2 = (NHJ 2 C0 3 . 

 Urea. Amnionic Carbonate. 



The changes in albuminoids produced by the pancreatic ferment and 

 in decomposition probably fall under this category. 



