ALIMENTARY CANAL STOMACH. 523 



The corium, averaging ^ of an inch thick, presents numerous 

 conical papilke, and consists, besides areolar tissue, of very many 

 longitudinal bundles of smooth muscular fibres. It also contains 

 fat cells and small racemose mucous glands. (Fig. 348.) 



The mucous membrane of the oesophagus is moderately sup- 

 plied with bloodvessels, lymphatics, and nerves. The last have not 

 yet been traced into the papilla. 



THE INFRA-DIAPHRAGMATIC PORTIONS OF THE ALIMENTARY 



CANAL. 



All the infra-diaphragmatic portions of the alimentary canal 

 (except a small part of the rectum) have still another layer ex- 

 ternal to the muscular coat, viz., the peritoneum. This serous mem- 

 brane forms a closed cavity; its epithelium being of the simple 

 scaly variety. Its corium is much thicker in the external or parie- 

 tal layer, than in the internal or visceral ; though having in both 

 the same structure like that of the corium of the skin. The 

 whole thickness of the membrane is 3^ to 2 ^ of an inch in the 

 latter case, and 3 J ff in the former. A loose sub serous layer of 

 areolar tissue containing fat-cells exists in most parts; not, however, 

 in the folds of the peritoneum. But few vessels or nerves are dis- 

 tributed to this membrane ; and lymphatics have been found only 

 in the sub-serous layer. 



Any peculiarity in the muscular coat will be specified in connec- 

 tion with the part in which it occurs. In general, it consists of an 

 incomplete layer of longitudinally arranged fasciculi of smooth 

 muscular fibres externally, and another of circular fibres internally. 

 The stomach has also a third layer of oblique fibres inside of the 

 circular layer. 



1. The Structure of the /Stomach. 



The mucous membrane of the stomach is reddish-gray, or bright 

 red during digestion, but at other times grayish. It is thinnest 

 (7*2 to 4\ f an inch) at the cardia; and thickest in the pyloric 

 region (^ E to T ^ of an inch). Little polygonal areas, ^ to ^ of an 

 inch across, bounded by very slight depressions, are not unfre- 

 quently found on the pyloric portion of the membrane. Dr. Neil 

 has shown that conical papilla exist around the pylorus, similar to 

 the villi of the small intestine, but smaller. 



The corium of the mucous membrane contains a layer of smooth 



