96 NUTRITION OF FARM ANIMALS 



pancreatic juice. The two processes go hand in hand. As 

 explained in Chapter I, the presence of free fatty acids favors 

 the formation of a permanent emulsion. As there noted, most 

 native fats contain small amounts of such acids which exist 

 dissolved in the natural fat. Furthermore, there seems to be 

 good evidence that some cleavage of fat into fatty acids and 

 glycerol takes place in the stomach of carnivora, while the di- 

 gestion of protein in the stomach helps to liberate any enclosed 

 fat. When the acid fats come in contact with the alkaline 

 pancreatic juice, the molecules of the free acid in solution are 

 saponified and in this way the mass of fat is broken up into an 

 emulsion. The action of the steapsin of the pancreatic juice, 

 which splits fat into glycerol and ^fatty acids, would obviously 

 tend to aid in the emulsification, while, on the other hand, the 

 latter, by vastly increasing the amount of surface exposed by the 

 fats, tends to aid the action of the enzyms. 



135. Saponification. The saponification of fat is accom- 

 plished essentially by the lipase steapsin of the pancreatic juice. 

 As just noted, the saponification is facilitated by the previous 

 emulsification, while the presence of the bile is also an important 

 factor. It is claimed that the presence of bile is necessary to 

 activate the steapsin, while it has also been shown that the 

 cleavage of the fats is much accelerated by the presence of bile, 

 the effect being ascribed to the lecithins which it contains. The 

 presence of bile also assists in the process of digestion by its 

 power of dissolving large quantities of fatty acids and of 

 their calcium and magnesium soaps. It appears also that the 

 bile aids in some way in the resorption of the fat, but just how 

 is not clear. 



Fats do not seem to be fermented to any extent in the diges- 

 tive tract and when administered to cattle in the form of emul- 

 sions have been found to produce no effect upon the excretion 

 of methane. When given in substance, they have in some in- 

 stances had the effect of diminishing the excretion of that gas. 



The digestion of the proteins and non-proteins 



136. Peptic digestion. In digestion the proteins are first 

 subjected in the stomach to the action of the pepsin and hy- 

 drochloric acid of the gastric juice. 



