MUCOUS COAT OF THE STOMACH. 



835 



The gastric mucous membrane is thickest in the pyloric portion of the 

 stomach, and thinnest in the great cul-de-sac. It always becomes thinner 

 in old age. 



The outer or adherent surface of the mucous membrane is connected with 

 the muscular coat by means of the intervening submucous layer so loosely 

 as to allow of considerable movement or displacement. In consequence of 

 this, and of the great extent and want of elasticity of the mucous membrane 

 as compared with the other coats, the internal surface of the stomach, when 

 that organ is in a contracted state, is thrown into numerous convoluted 

 ridges, rugce, which are produced by the wrinkling of the mucous, together 

 with the areolar coat, and are entirely obliterated by distension of the 

 stomach. These folds of the mucous coat are most evident along the great 

 curvature, and have a general longitudinal direction. 



On examining the gastric mucous membrane closely with the aid of a 

 simple lens, it is seen to be marked throughout, but more plainly towards 

 the pyloric extremity, with small depressions or cells named alveoli, which 

 have a polygonal figure, and vary from about -^^th to -j-^th of an inch 

 across, being larger and more oblong near the pylorus. 



Fig. 582. ENLARGED VIEW OF A SMALL PART OF THE SUR- Fig. 582. 



FACE OP THE MUCOUS MEMBRANE OF THE STOMACH (from 



Ecker). ia 



This specimen shows the shallow alveoli, in each of which 

 the smaller dark spots indicate the orifices of a variable num- 

 ber of the gastric glands. 



Towards the pyloric region of the stomach, where 

 the mucous membrane is thicker than elsewhere, the 

 margins of these alveoli are elevated into pointed 

 processes or fringes, which may be compared to rudimentary vtili, the 



Fig. 583. 



Fig. 583. VERTICAL TRANSVERSE SECTION OP THE 

 COATS OP A PIG'S STOMACH (from Kolliker). ^- 



a, gastric glands ; 6, muscular layer of the 

 mucous membrane ; c, submucous or areolar coat ; 

 d, circular muscular layer ; c } longitudinal mus- 

 cular layer ; /, serous coat. 



perfect forms of those appendages existing 

 only in the small intestine, and making 

 their appearance in the duodenum, imme- 

 diately beyond the pylorus. 



At the bottom of the alveoli, and also in 

 the intervals between them, are seen small 

 round apertures, which are the mouths of 

 minute tubes, placed perpendicularly to the 

 surface, closed at their attached or deep 

 extremity, which rests on the submucous 

 areolar tissue, and opening at the other on 

 the inner surface of the stomach. On mak- 

 ing a vertical section of the membrane, and 

 submitting it to microscopic examination, 

 it is seen to consist almost entirely of these small tubuli, arranged close 

 to and parallel with each other. Their diameter varies from T ^ D th to ^-g^th of 



3 i 2 



