470 



THE DIGESTIVE APPARATUS IN MAMMALIA. 



smaller leaves there appears to be only one layer of muscular fibres ; on all the leaves are 

 various-sized papillae, the smallest of which are like a grain of millet, and have for base a 

 mass of condenser! connective tissue, the superficial fibres of which form a kind of shell (Fig. 

 273) ; the largest are club-shaped. They receive blood-vessels, and we have found in the 

 connective tissue which constitutes their basis, elements with a somewhat irregular outline, 

 provided with nuclei, which we considered to be nerve-cells (Fie;. 274). 



The omasum in the Camel shows deep areolae instead of leaves, and the openijjg with 

 the abomasum is relatively very narrow. 



Abomascm (Reed or Renxet. Figs. 268, 269, 270, 271). Situation— Form — Relations. — 

 The abomasum stands next to the rumen for capacity. It is a pyriform reservoir, curved on 

 itself, elongated from before to beliind, and situated behind the omasum, above the right sac 

 of the rumen. On the right it touches the diaphragm and the hypochondriac ; on the left it 

 is related to the rumen. The greater curvature, turned downwards, receives the insertion of 

 the great omentum. The lesser curvature, inclined upwards, gives attachment to the serous 

 band already noticed when speaking of the great curvature of the omasum. Its base is in 

 contact with the cul-de-sac of the reticulum, and is separated from the omasum by the con- 

 striction in tlie form of a thick neck, which corresponds to the communicating oritice of the 

 two stomachs. Its point, directed upwards and backwards, is continued by the duodenum. 



Interior. — This being the true stomach of Ruminants, tlie mucous membrane lining its 

 interior acquires all the characters which distinguish that of the stomach of the Carnivora, 

 or that of the right sac of the Horse's stomach. It is soft, spongy, smooth to the touch, 

 vascular, red-coloured, covered by a thin epithelium, and provided with numerous glands for 



SECTION OF A LEAF OF THE OMASUM. 



1, 1, Muscular planes; V, vessel; 2, epithe- 

 lium; 3, 3, small-sized papillae, round and 

 hard. 



LONGITUDINAL SECTION OF A LARGE PAPILLA 

 FROM THE OMASUM, SHOWING NERVE-CELM 

 IN ITS INTERIOR. 



the secretion of the gastric juice. Thinner than in monogastric animals, this tenuity is com- 

 pensated for by a much greater extent of surface, which is still further increased by numerous 

 lamellar folds. These latter are analogous in constitution to tliose of the omasum, cross in a 

 very oblique manner the great axis of the abomasum, and altogether affect a kind of spiral 

 arrangement. 



The abomasum has two openings : one, situated at its base, opens into the omasum ; the 

 other, placed opposite to the first, and much narrower, is the pylorus, which is circumscribed, 

 as in the other animals, by a muscular ring. 



Structure. — The serous membrane is continuous with the omenta tiiat abut on the great and 

 lesser curvatures of the viscus. The muscular layer is of the same thickness as in the omasum. 

 The internal tunic has already been noticed. 



Functions of the Stomach in Ruminants. — We cannot pretend to give here a complete 

 history of the phenomena of rumination, but must confine ourselves to describe in a few words 

 what are the principal attributes of each gastric dilatation. 



The rumen is a sac where the aliment taken during feeding-time is kept in reserve, and 

 whence it is again carried into the mouth during rumination, after having been more or less 

 softened. 



The reticulum participates in the functions of the rumen, to which it is only a kind of 

 diverticulum. But it is particularly with regard to liquids that it plays tlie part of a reservoir ; 

 the solid sub.stauces contained in it being always diluted by a large quantity of water. 



The oesophageal groove carries into the omasum the substances swallowed a second time 

 after rumination, or even those which the animal ingests in very small quantity for the first 

 time. 



