Mesentery 



325 



determine peritonitis. The typhoid ulceration, like the Peyer's patch, 

 has its long axis with that of the bowel, whilst tubercular ulceration 

 generally extends across the long axis, that is, in the direction of the 

 blood-vessels which encircle the bowel. 



A special outgrowth, iWeckel's diverticulum, is found about 2 ft. 

 above the ileo-caecal valve : it is the remnant of an early fcetal 

 canal, the vitelline duct, which extended from the interior of the ileum 

 through the umbilicus ; a loop of intestine is occasionally strangled 

 around it or its remnant Persistence of the duct may cause umbilical 

 fistula, or may involve a fatal snaring of a coil of bowel. 



The arteries of the small intestine are the superior and inferior pan- 

 creatico-duodenal (from the hepatic and 

 superior mesenteric) and vasa intestini 

 tenuis (superior mesenteric). The pan- 

 creatico-duodenal, or the gastro-duodenal 

 (hepatic), is occasionally implicated in 

 duodenal ulcer following a severe burn. 

 The veins pass by the superior mesenteric 

 vein into the vena portse. The lacteah 

 and lymphatics course between the layers 

 of the mesentery to end in glands at its 

 base. The nerves come from the aortic 

 plexus of the sympathetic along the 

 mesenteric artery, together with pneumo- 

 gastric filaments. 



On opening the abdomen in the case 

 of intestinal obstruction absolute size of 

 bowel is no guide to its recognition, for 

 small intestine may be distended to the 

 size of the forearm whilst the colon may 

 be no larger than the thumb. Also when 

 the colon is distended its three longitu- 

 dinal bands of muscular fibres are temporarily effaced. But the large 

 intestine may always be recognised by the presence of appendices 

 epiploicse, of which the small intestine is entirely destitute. The colon 

 may also be recog'nised by its comparatively fixed position in the lateral 

 and upper transverse parts of the abdomen. 



The ileum occasionally shows offshoots, nearly as large as the 

 bowel itself, called cUverticula ; structurally they resemble the parent 

 bowel. They are generally hernial protrusions of the mucous mem- 

 brane through the muscular coat. 



The mesentery (/Liecro?, middle ; ei/repa, bowel) is the thin doubling 

 of peritoneum by which the jejunum and ileum are surrounded, and 

 are hung from the vertebral column ; blood-vessels, lymphatics, and 

 nerves course between its layers. Its attached end is from four to six 

 inches wide, and slopes from the left side of the second lumbar vertebra 



l>, duodenal ulcer after burn ; a, 

 pylorus ; c and d, bristles passed 

 through ulcerations in pancrea- 

 tico-duodenal arteiy and vein. 

 (HOLMES.) 



