374 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



partially digested in the stomach, and its subsequent changes completed 

 in the intestines. Consequently, oats should always succeed the admin- 

 istration of hay in the feeding of horses. So, also, water should not be 

 given after a meal of oats to the horse, or else it will wash the oats out of 

 the stomach before digestion is completed. Consequently, the water 

 should precede haj, and both hay and water should precede the admin- 

 istration of oats. 



The short time that food remains in the stomach is probably the 

 reason that the horse does not readily'digest animal food, although in 

 the Tartar steppes it is stated that horses become accustomed to a meat 

 diet. 



In addition to true digestion, fermentative processes also occur in 

 the stomach, especially in the earlier stages of gastric digestion, when 

 the hydrochloric acid is absent or present only in small amounts. It 

 has been shown that hydrochloric acid is always in small amount in 

 the oesophageal sac, and in this locality lactic acid fermentation, as well 

 as fermentation of cellulose, undoubtedly may occur, though the time 

 which the food remains in this part of the stomach is too short to permit 

 of any extensive change of this character. It will be subsequently shown 

 that the conditions for the fermentation of cellulose are much more favor- 

 able in the intestinal canal of the horse than in the stomach. 



7. Gastric Digestion in Ruminants. — Gastric digestion, which has 

 been found to be much the same in carnivora and solipedes, takes on 

 a new form in the ruminant animals, and although the general result of 

 gastric digestion is the same in all, special means are concerned in the 

 accomplishment of this result in the ruminant that are not seen in ani- 

 mals with a simple stomach. This complication is practically due to the 

 preliminary and accessory changes which occur in the food before it is 

 subjected to the action of gastric juice. Hence, the changes in the first 

 three compartments of the stomach are without an analogue in the gastric 

 digestion of monogastric animals, while the fourth stomach reproduces 

 exactly the process that takes place in this viscus of the latter class of 

 animals. 



Although the four gastric reservoirs of the ruminant are anatomi- 

 cally connected, they are, to a certain point, functionally isolated, each 

 one of them having tolerably distinct functions to fulfill. The first three 

 are concerned in the storing of foods and liquids in rumination, while in 

 the fourth alone true digestion takes place. This ma}^ occur during 

 rumination or during inaction of the first three stomachs. 



The rumen receives almost all of the aliments when swallowed for 

 the first time, the greater part of liquids drunk, and a considerable 

 portion of the results of the second mastication (Fig. 153). It keeps 

 them stored up for a certain time in its interior, where they become thor- 



