572 ZOOLOGY SECT. 



raised up into a number of anastomosing ridges, giving its wall 

 the appearance of a honeycomb with shallow cells. From the 

 aperture by which the reticulum communicates with the rumen 

 .to that with which it communicates with the psalterium, runs 

 a groove bounded by a pair of muscular ridges, which are capable 

 of closing together in such a way as to convert the groove into 

 a canal. The mucous membrane of the psalterium (d) is raised 

 up into numerous longitudinal leaf-like folds. The abomasum 

 (e), smaller than the rumen, but larger than the reticulum, has 

 a smooth, vascular and glandular mucous membrane. The oeso- 

 phagus opens into the rumen close to its junction with the 

 reticulum. The herbage on which the Ruminant feeds is swal- 

 lowed without mastication, accompanied by copious saliva, and 

 passes into the rumen and reticulum, where it lies until, having 

 finished feeding, the animal begins ruminating or chewing the 



FIG. 1199.- Stomach of Ruminant opened to show the internal structure, a, oesophagus ; 

 b, rumen ; c. reticulum ; d. psalterium ; e, abomasum ; /, duodenum. (After Flower and 

 Lydekker.) 



cud. In this process the sodden food is returned in rounded 

 boluses from the rumen to the mouth, and there undergoes 

 mastication. When fully masticated it is swallowed again in a 

 semi-fluid condition, and passes along the groove into the reti- 

 culum, or over the unmasticated food contained in the latter 

 chamber, to strain through between the leaves of the psalterium 

 and enter the abomasum, where the process of digestion goes on. 

 In some Ruminants the psalterium is wanting. In the Camels 

 (Fig. 1198, G) the stomach is not so complicated as in the more 

 typical Ruminants, there being also no distinct psalterium, and 

 the rumen being devoid of villi ; both the rumen and the 

 reticulum have connected with them a number of pouch-like 

 diverticula (w. z.\ the openings of which are capable of being 

 closed by sphincter muscles ; in these water is stored. In the 

 Cetacea the stomach is also divided into compartments. In the 

 Porpoise (Fig. 1200) the oesophagus (a) opens into a spacious 



