DISSECTION OF THE ABDOMEN. 



329 



circular layer is found all over the organ, but the other layers are 

 mainly confined to the left half At the right extremity of the stomach 

 the circular fibres are aggregated to form 

 the sphincter-like pyloric ring. The fibres 

 are of the non-striped variety. 



3. The SuhmucoiLs Coat is composed of 

 areolar connective-tissue, in which the 

 blood-vessels ramify before they pass into 

 t he next coat. 



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 duo- 

 denum and a few inches of the oeso- 

 phagus 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 

 guUet, although that is unligatured. This 

 is an instructive experiment, as showing 

 the difficulty or impossibility of vomition in 

 the horse. Now allow the contents 

 of the stomach to escape by the duo- 

 denum ; 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 difierent 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 squamous epithelium. 

 It is, in fact, an extension of the oesophageal mucous membrane, 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 mem- 

 brane. 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 rugm. 



The CEsoPHAGBAL Oeificb, it will now be seen, is very narrow, and 

 obstructed by the mucous membrane gathered into folds. 



Fig. 38. 



Vertical Transverse Section op 

 THE Coats of a Pig's Stomach. 

 30 Diameters (from Kolliker). 

 a. Gastric glands ; b. Muscular layer 

 of the mucous membrane ; c. Sub- 

 mucous or areolar coat ; d. Circular 

 muscular layer ; e. Longitudinal mus- 

 cular layer ; /. Serous coat. 



