THE SMALL INTESTINE 



361 



cavity of the second curve, and here, five to six inches (ca. 12 to 15 cm.) from the 

 pylorus, the pancreatic duct and the bile duct pierce the bowel wall. The second 

 part passes upward and backward on the right lobe of the liver and, on reaching 

 the right kidney and the basc^ of the ciecum, it curves toward the median plane, 

 opposite the last rib. The third part passes almost transversely from right to 

 left behind the base of the caecum, crosses the median plane under the third and 

 fourth lumbar vertebrse, and turns forward to become continuous with the jejunum 

 under the left kidney. The sacculations of the first part have a diameter of three 

 to four inches (ca. 7.5 to 10 cm.). 



It is attached by a short peritoneal fold termed the mesoduodenum. This 

 fixes the first part of the duodenum closely to the liver and the right dorsal part 

 of the colon; the remainder is somewhat less closely attached by it to the caecum 



Fig. 263. — Topocraphy of Viscera of Horse, Left View. 

 I.R., First thoracic vertebra; I.L., first lumbar vertebra; 2.K., second sacral spine; S., scapula; .1., 

 humerus; St., sternum; S., ilium; O., femur; L., lung in complete expiration; ?., dotted line indicating contour of 

 lung in inspiration; //.pericardium; Z, costal part of diaphragm; .Z', tendinous center of diaphragm; L.V., left 

 kidney; l.v.C, left ventral colon; v.Q., sternal flexure of colon; d.Q., diaphragmatic flexure of colon; />., small 

 intestine; M., small colon; M' , rectum; a, coccygeus muscle; h, retractor ani; c, c , sphincter ani externus; d, 

 constrictor vulvae; e, sacro-coccygeus inferior; /, anterior gluteal artery; g, internal pudic artery; h, abdominal 

 wall in section. (After EUenberger, in Leisering's .\tlas. reduced.) 



and right kidney, the sul)luml)ar muscles, and (more closely) to the terminal part 

 of the great colon and the first part of the small colon. ^ 



The jejunum and ileum together (Jejuno-ileum) constitute the mesenteric or 

 floating portion of the small intestine. No chstinct point exists at which to make 

 the demarcation. With the exception of the last two or three feet, the mesenteric 

 part of the intestine varies so much in position that only a general statement can 

 be made. It lies in numerous coils (Ansae) mingled with those of the small colon, 

 chiefly in the dorsal part of the left half of the abdomen, from the visceral surface 

 of the stomach to the pelvis. It may insinuate itself between the left portions of 

 the colon and the abtlominal wall; also between the ventral portions of the colon, 

 reaching the floor of the abdomen. The terminal part of the intestine (ileum) 

 ascends almost vertically, a little to the right of the median plane, to open into the 



^ It will be noticed that the mesoduodenum is not continuous with the great mesentery, but 

 ends by a free edge. The mesentery begins on the opposite surface of the end of the duodenum, 

 so that the bowel is attached by two peritoneal folds at this point. 



