340 



THE ANATOMY OP THE HORSE. 



4. The Mucous Coat. — It is desirable to study this on the stomach of 

 an animal recently killed. If possible, take such a stomach with about 

 a foot of the duodenum and a few inches of the oesophagus attached, and 

 fasten the duodenum to a tap. Let water flow into the organ, and it 



will be noticed that, even when the 

 stomach is much distended, none of the 

 water escapes by the orifice of the gullet, 

 although that is unligatured. This is 

 an instructive experiment, as showing 

 the difficulty of vomition in the horse. 

 Now allow the contents of the stomach 

 to escape by the duodenum ; and either 

 evert the organ and inflate it, or incise 

 it along its convex curvature. It will 

 at once be noticed that the mucous 

 lining is not the same throughout. The 

 left or cardiac half of the cavity is lined 

 by a mucous membrane termed cuticular ; 

 the right or pyloric half has a totally 

 different lining, termed villous. The 

 cuticular portion is pale, harsh, without 

 true gastric glands, but possessed of a 

 few mucous follicles, and covered on its 

 free surface by a thick stratified squam- 

 ous epithelium. It is, in fact, an ex- 

 tension of the oesophageal mucous mem- 

 brane, which it resembles in all respects. Towards the middle of the 

 stomach it is separated from the villous half by an abrupt, raised, and 

 slightly sinuous line of demarcation — the cuticular ridge. The villous 

 half is rosy, soft, and velvety (but without villi), thickly beset with 

 gastric glands, and possessed of a single layer of columnar epithelium. 

 The gastric glands are of the tubular variety, and by the aid of a lens 

 numbers of them may be seen opening together into pits, or alveoli, of 

 the mucous membrane. The cuticular portion is but slightly vascular, 

 but the villous portion is richly supplied with blood-vessels. In the 

 collapsed organ the mucous membrane is thrown into folds, or j-ugw. 



The (Esophageal Orifice, it will now be seen, is very narrow, and 

 obstructed by the mucous membrane gathered into folds. 



The PrLORic Orifice is much larger, and in the horse it appears to 

 be never quite closed, notwithstanding the presence of the pyloric ring 

 of circular fibres around it. 



In the interior of the duodenum, about six inches from the pylorus, 

 the openings of the bile and pancreatic ducts will be found. The 

 orifices of the bile duct and duct of Wirsung are placed together on the 



Fig. 44. 

 Vertical Tranhverse Section of the 

 Coats of a Pig's Stomach. 30 

 Diameters (from KoUiker). 

 a. Gastric glands ; b. Muscular layer 

 of the mucous membrane ; c. Submucous 

 or areolar coat ; d. Circular muscular 

 layer ; e. Longitudinal muscular layer ; 

 /. Serous coat. 



