STRUCTURE OF THE LARGE INTESTINE 



431 



thick and consists of large bundles which are rather loosely united. A large band, 

 the recto-coccygeus, is detached from it on either side, and passes upward and 

 backward to be inserted into the fourth and fifth coccygeal vertebra. 



The submucous tissue is abundant in the wall of the rectum, so that the mucous 

 membrane is loosely attached to the muscular coat, and forms numerous folds 

 when the bowel is empty. 



The mucous membrane of the large intestine is thicker and darker in color 

 than that of the small intestine. It forms large crescentic or semilunar folds 



Fig. 370. — Pelvic Inlet and Posterioh Part of Abdominal Wall of Horse, Viewed from the Front. 

 The left inguinal canal is partially opened. The peritoneum ia retained except over a part of the left cremaster 

 Jnu3cle. The sublumbar region is greatly foreshortened in this view, a, a', Kidneys; a", adrenal; b., ureter; c, renal 

 artery; d, aorta; e, stump of cceliac artery; /, stump of anterior mesenteric artery; 9, posterior mesenteric 

 artery; h, circumflex iliac artery; i, external iliac artery; k, internal iliac artery; Z, spermatic artery in peritoneal 

 fold (plica vasculosa), m; n, ductus deferens, enclosed in genital fold, o; p, urinary bladder; q, round Hgament of blad- 

 der; r, middle ligament of bladder; s, rectum; t, margin of vaginal ring; u, posterior abdominal artery; v, external 

 pudic artery; w, rectus abdominis muscle; x, transversus and obliquus internus abdominis; y, y', cremaster externus; 

 z, posterior vena cava (cut). (After Ellenberger-Baum, Top. Anat. d. Pferdes.) 



(Plicae semilunares) , corresponding to the external constrictions. It has no villi 

 nor duodenal glands. The intestinal glands are large and numerous. Solitary 

 nodules are numerous, and there are aggregated l3rmph nodules at the apex of the 

 csecum and in the pelvic flexure and the adjacent portion of the left dorsal part of 

 the colon. 



Vessels and Nerves. — The arteries come from the anterior and posterior 

 mesenteric and internal pudic arteries. The veins go to the portal and internal 

 pudic veins. The lymph vessels of the csecum and colon go to the caecal and colic 

 lymph glands, thence to the cisterna chyli. Those of the rectum go to the internal 



