888 



THE DIGESTIVE APPARATUS IN MAMMALIA. 



Fig. 184. 



Tha right extremity, lower than the left, touches the right lobe of the liver 

 and the above-mentioned intestinal curvatures. 



Interior. When a stomach is opened to study its interior, one is at first 

 struck by the different aspect its internal membrane presents, according as 

 it is examined to the right or left. To the left, it has all the characters of 

 the cesophageal mucous membrane, in being white, harsh, and even resisting ; 

 it is covered by a thick layer of epithelium. To the right, it is thick, 

 wrinkled, spongy, very vascular and follicular, has a reddish-brown tint 

 which is speckled by darker patches, loses its consistency, and is deprived 

 of the remarkable epidermis it exhibits on the left side, to be covered by 

 a very thin epithelial pellicle. It is not by an insensible, but a sudden 

 transition that the mucous membrane of the stomach is thus divided into 



two portions ; and their separation is in- 

 dicated by a salient, more or less sinuous, 

 and sharply-marked ridge. This crest, 

 then, divides the stomach into two com- 

 partments : a division already indicated 

 externally by the circular depression 

 observed in the majority of subjects. 

 The left sac or compartment is considered 

 as a dilatation of the oesophagus. The 

 right sac constitutes the true stomach of 

 Solipeds ; as on it alone devolves the 

 secretory function which elaborates the 

 gastric juice, the essential agent of diges- 

 tion in this organ. 



The interior of the stomach (Fig. 

 184) offers for study two apertures : the 

 cardiac and pyloric. The cardiac, or 

 ossopJiageal orifice, is in the lesser curva- 

 ture of the left sac of the stomach. Its 

 disposition has given rise to numerous 



discussions, as in it has generally been sought the reason why Solipeds 

 vomit with such extreme difficulty. At one time there has been des- 

 cribed a semilunar or spiroidal valve, which is opposed to the retrograde 

 movement of the food ; and at another time it was the oblique insertion of 

 the oesophageal canal, resembling that of the ureters into the bladder, and 

 which, by a mechanism analogous to these, proved an obstacle to the return 

 of aliment into the oesophagus. Both suppositions are wrong. When we 

 attentively observe the manner in which the oesophagus comports itself at 

 its termination, it will be noticed that it is inflected downwards, after travers- 

 ing the right pillar of the diaphragm, and is inserted almost perpendicularly 

 into the lesser curvature of the stomach. In opening- into this viscus, 

 the oesophagus does not widen into an infundibulum, as in other animals ; 

 on the contrary, its calibre is here narrower than elsewhere, and its cardiac 

 or stomachal orifice, completely obstructed by the folds of mucous membrane, 

 only occupies an infinitely small portion of the internal surface of the 

 stomach. 



With regard to the pylorus, it represents a large aperture formed at the 

 bottom of the right sac, and furnished with a thick circular ring; this 

 opening can be completely closed through the action of the powerful 

 sphincter surrounding it. 



STRUCTURE. The parietes of the stomach are composed of three 



INTERIOR OF THE HORSE'S STOMACH, 



A, Left sac; B, Right sac; C,. Duodenal 

 dilatation. 



