THE GREAT COLON 



365 



the preceding one; the interval between them is only about two inches (ca. 5 cm.), 

 and they are separated by a distinct ridge which projects into the interior of the 

 caecum. The orifice is slit-like and is small in relation to the size of the caecum 

 and colon. It has a valvular fold (Valvula caicocolica) at its lower margin and a 



Fig. 267. — Topography of Visrp:RA of Horse, Right Vikw. 

 7i?., First thoracic vertebra; iL., first lumbar vertebra; .2/v., second sacral spine; S., scapula; ^..humerus; 

 <S7., sternum; .B., ilium; O., femur; L., right lung; //., pericardium; Z., diaphragm (pars costalis); r.v.C, right 

 ventral colon; r.Q., sternal flexure of colon; c?.(^., diaphragmatic flexure of colon; C, body of ca'cum; C, base of 

 csecum: C" ., apex of caecum; D., small intestine; F., pelvic flexure of colon; M., rectum; a., abdominal wall in 

 section; h, duodenum; c, coccygeus muscle; d, retractor ani; e. e' , sphincter ani externus; /, anterior gluteal ar- 

 tery; f/, internal pudic artery; h, xiphoid cartilage. (After Ellenberger, in Leisering"s Atlas.) 



muscular ring (Sphincter cseci). Large crescentic or semilunar folds (Plicae caeci) 

 project into the cavity of the l)owel, and l^etween these are large pouches (Cellulse 

 caeci). 



Vessels and Nerves. — The caecal arteries come from the great mesenteric 

 artery. The veins go to the portal vein. 

 The nerves are tlerived from the great ? 



mesenteric plexus of the sympathetic. 



The Great Colon 

 The great colon (Colon crassum) begins 

 at the caeco-colic orifice, and terminates by 

 joining the small colon behind the saccus 

 caecus of the stomach. It is ten to twelve 

 feet (ca. 3 to 3.7 m.) long, and its average 

 diameter (exclusive of its narrowest part) is 

 about eight to ten inches (ca. 20 to 25 

 cm.). Its capacity is more than double 

 that of the caecum. When removed from the abdomen, it consists of two parallel 

 portions, which are connected by peritoneum and partially by areolar tissue also. 

 In situ, it is folded so that it consists of four parts, which are designated according 

 to their position or numerically. The three bent connecting parts are termed 



Fig. 268. — Ileo-c^cal Orifice of Horse. 

 a, Mucous membrane of coecum; 6, ileum; 

 c, ileo-cffical orifice; rf, fold of mucous membrane. 

 (After P. Schumann.) 



