Both jejunum and ileum are supplied by the superior mesenteric, from which some fifteen to twenty branches run forward between the mesenteric layers, form numerous anastomosing arches, and then give off little straight vessels which run forward to the bowel, and then bifurcate at the mesenteric attachment, one little vessel running along either side of the bowel wall, first subperitoneally, and then in the submucous coat. The veins are similarly arranged, and run to join the superior mesenteric which, joining with the splenic, forms the portal vein. The lymphatics, or lacteals, as they are here called, commencing in the villi of the mucous membrane, and as lymphatic sinuses surrounding the bases of the solitary glands, form plexuses between each of the coats, submucous and subserous, and also between the two muscular coats, then pass between the mesenteric layers to the mesenteric glands (which may number over 1oo, the larger ones lying close to the mesenteric attachment), and then, uniting to form one or more large vessels, open into the RECEPTACULUM CHYLI, which lies on the right side of the body of the second lumbar vertebra. In tubercular disease of the intestine the infection is frequently carried to these mesenteric glands, causing taņes mesenterica. The glands may become very large, and caseate, or, later, they may form large calcareous masses. The mesentery may shrink, causing peritonitis deformans, and even in less severe cases, symptoms resembling intestinal obstruction frequently arise. Chyle cysts, which may attain a large size, arise probably from blocking of some of the ducts. The nerves are derived chiefly from the solar plexus, a few fibres coming from the right vagus, and pass as the superior mesenteric plexus, along with the superior mesenteric artery, to the bowel, where they form intermuscular (Auerbach's) and submucous (Meis-sner's) plexuses.
Meckel's diverticulum is produced by persistence of the intestinal end of the vitello-intestinal duct ; is situated on the ileum, some 1 to 4 feet from the ileo-caecal valve ; and consists of a diverticulum of varying length, but generally only a few inches long, of the same structure and calibre as the bowel from which it springs. It may terminate in a free extremity, or may be continued toward the umbilicus as a fibrous cord. It is met with in about 2 per cent, of bodies, and is chiefly of importance from its tendency to cause intestinal obstruction : by twisting round some other portion of bowel ; from its tip becoming adherent, and a loop of bowel slipping under the bridge so formed ; from contraction of its adhesions, dragging upon and kinking the ileum from which it springs ; or, by causing intussusception.