378 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



found in this stomach after death is alwa}~s dry. The mucous membrane 

 is, however, entirely incapable of absorption, and the dryness of its 

 contents cannot, therefore, be explained as due to the entrance of the 

 fluid from its contents into the blood. The psalter likewise furnishes no 

 secretion of its own, and the changes which occur in its contents are due 

 simply to the influence of the saliva and the fermentative process which 

 occurs in the two preceding stomachs. Its reaction is, however, often 

 acid, evidently due to the regurgitation of the fluids from the fourth 

 stomach. It is worthy of note that in the llama, the camel, and, to a 

 less extent, in the sheep the folds of the membrane in the third stomach 

 are but slightly developed, and there is no constriction between the third 

 and fourth stomachs, while the opening into the reticulum is particularly 

 narrow. This may possibly serve to prevent too great dryness of the 

 contents of this compartment in these animals, which are so frequently 

 deprived of water. Where obstruction of the stomach occurs, it is 

 nearly always to be found in this compartment. 



The action of the first three stomachs is merely preparatory to 

 digestion. It is only in the fourth stomach that true digestion takes 

 place. Its secreting membrane is four or five times as extensive as that 

 of the right half of the stomach of the horse, and is relatively less in the 

 llama and dromedary than in other ruminants. The gastric secreting 

 membrane is, apparently, in all respects similar to what has already been 

 described in other animals, although the amount of pepsin and acid in 

 the gastric juice of ruminants is less than that found in this secretion of 

 carnivora. Pauli states that extracts made from the glandular portion 

 of the fuiidus of the fourth stomach of the ox possess a much greater 

 digestive power than similar extracts made from the pylori c portion ; 

 in other words, the amount of acid added being the same in both cases, 

 that the glands of the pylorus are poor in pepsin, the glands of the fund us 

 rich in pepsin ; and that the small amount of pepsin in the pyloric por- 

 tion is almost incapable of extraction with gtycerin, but is removed by 

 hydrochloric, acid and by common salt solutions. Pauli would infer 

 from these statements that, the histological structure of the ruminant's 

 stomach being similar to that of other mammals, the so-called chief cells 

 are not the peptic cells, but perhaps are .concerned in the elaboration of 

 other ferments, while the associate cells are the true peptic cells. We 

 have alreacty in another place discussed the grounds for attributing the 

 acid of the gastric juice to the action of the associate cells. 



Since the aliments enter the stomach but slowly and graduall} r , and 

 some already in a fluid state, digestion in the stomach occurs under the 

 most favorable circumstances, and is rapidly completed. The pylorus is 

 narrow and guarded by a powerful sphincter, thus resembling that of 

 carnivora in contradistinction of what has been noticed in the horse, and 



