. The anatomy of the domestic animals . Veterinary anatomy. THE SMALL INTESTINE 421 Hepatic'^ duct Pancreo/ic duct between which the vessels and nerves reach the bowel; it also contains the mesen- teric lymph glands and some fat. The visceral border of the mesentery contains the intestine, while the parietal border or root of the mesentery (Radix mesenterii) is attached to a small area around the great mesenteric trunk under the first and second lumbar vertebrae. The root is thick, as it contains a large nmnljer of vessels and nerves placed close together. The mesentery is short at first, but
. The anatomy of the domestic animals . Veterinary anatomy. THE SMALL INTESTINE 421 Hepatic'^ duct Pancreo/ic duct between which the vessels and nerves reach the bowel; it also contains the mesen- teric lymph glands and some fat. The visceral border of the mesentery contains the intestine, while the parietal border or root of the mesentery (Radix mesenterii) is attached to a small area around the great mesenteric trunk under the first and second lumbar vertebrae. The root is thick, as it contains a large nmnljer of vessels and nerves placed close together. The mesentery is short at first, but soon reaches a length of one and a half to two feet (ca. 50 cm.)—sufficient to allow coils of the intestine to reach the abdominal floor, the pelvic cavity, or even to descend into the scrotum through the inguinal canal. Near its termination the intestine leaves the border of the mesentery, so that the latter has a free edge which passes to the csecum. Thus there is formed the ileo-csecal fold (Plica ileocajcalis), which at- taches the ileum to the lesser curvature of the caecum. Structure.—The wall consists of four coats—serous, muscular, submucous, and mucous. The serous coat is complete except at the mesenteric edge, where the vessels and nerves reach the bowel. The muscular coat consists of an external longitudinal and an internal circular layer, the latter being the thicker. In the last few feet of the intestine the muscular coat is very thick, and being usually firmly contracted in the dead subject, gives the impression that this part of the bowel is of smaller caliber; such, however, is not the case during life. The sub- mucous coat is a layer of areolar tissue in which the vessels and nerves ram- ify. It contains also the duodenal glands and the bases of the solitary and aggregated IjTnph nodules. The mucous membrane is soft and vel- vety. It has a grayish or yellowish- red color and is very vascular. About five or six inches from the pylorus it forms a pouch, the
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