THE LARGE INTESTINE 



1187 





the sacculi. In the rectum it is thicker, of a darker color, more vascular, and connected loosely 

 to the muscular coat, as in the esophagus. 



As in the small intestine, the mucous membrane (Fig. 1082) consists of a muscular layer, the 

 muscularis mucosse; a quantity of retiform tissue in which the vessels ramify; a basement mem- 

 brane and epithelium which is of the columnar variety, and resembles the epithelium found in 

 the small intestine. The mucous membrane of the large intestine presents for examination glands 

 and solitary lymphatic nodules. 



The glands of the great intestine are minute tubular prolongations of the mucous membrane 

 arranged perpendicularly, side by side, over its entire surface; they are longer, more numerous, 

 and placed in much closer apposition than those of the small intestine; and they open by minute 

 rounded orifices upon the surface, giving it a cribriform appearance. Each gland is lined by 

 short columnar epithelium and contains numerous goblet cells. 



The solitary lymphatic nodules (noduli lymphatic solitarii) (Fig. 1082) of the large intestine 

 are most abundant in the cecum and vermiform process, but are irregularly scattered also over 

 the rest of the intestine. They are similar to those of the small intestine. 



Vessels and Nerves. The arteries supplying the colon are derived from the colic and sigmoid 

 branches of the mesenteric arteries. They give off large branches, which ramify between and 

 supply the muscular coats, and after dividing into small vessels in the submucous tissue, pass 

 to the mucous membrane. The rectum is supplied by the superior hemorrhoidal branch of the 

 inferior mesenteric, and the anal canal by the middle hemorrhoidal from the hypogastric, and 

 the inferior hemorrhoidal from the internal pudendal artery. The superior hemorrhoidal, the 

 continuation of the inferior mesenteric, divides into two branches, which run down either side 

 of the rectum to within about 12.5 cm. of the anus; they here split up into about six branches 

 which pierce the muscular coat and descend between it and the mucous membrane in a longi- 

 tudinal direction, parallel with each other as far as the Sphincter ani internus, where they anas- 

 tomose with the other hemorrhoidal arteries and form a series of loops around the anus. The 

 veins of the rectum commence in a plexus of vessels which surrounds the anal canal. In the 

 vessels forming this plexus are smaller saccular dilatations just within the margin of the anus; 

 from the plexus about six vessels of considerable size are given off. These ascend between the 

 muscular and mucous coats for about 12.5 cm., running parallel to each other; they then 

 pierce the muscular coat, and, by their union, form a single trunk, the superior hemorrhoidal 

 vein. This arrangement is termed the hemorrhoidal plexus; it communicates with the tribu- 

 taries of the middle and inferior hemor- 

 rhoidal veins, at its commencement, 

 and thus a communication is estab- 

 lished between the systemic and portal 

 circulations. The lymphatics of the large 

 intestine are described on page 711. 

 The nerves are derived from the sym- 

 pathetic plexuses around the branches 

 of the superior and inferior mesenteric 

 arteries. They are distributed in a 

 similar way to those found in the small 

 intestine. 



Congenital Hernia. There are some 

 varieties of oblique inguinal hernia 

 (Fig. 1084) depending upon congenital 

 defects in the saccus vaginalis, the pouch 

 of peritoneum which precedes the 

 descent of the testis. Normally this 

 pouch is closed before birth, closure 

 commencing at two points, viz., at the 

 abdominal inguinal ring and at the top 

 of the epididymis, and gradually ex- 

 tending until the whole of the inter- 

 vening portion is converted into a 

 fibrous cord. From failure in the com- 

 pletion of this process, variations in the 

 relation of the hernial protrusion to the 

 testis and tunica vaginalis are pro- 

 duced; these constitute distinct varieties of inguinal hernia, viz., the hernia of the funicular 

 process and the complete congenital variety. 



Where the saccus vaginalis remains patent throughout, the cavity of the tunica vaginalis 

 communicates directly with that of the peritoneum. The intestine descends along this pouch 

 into the cavity of the tunica vaginalis which constitutes the sac of the hernia, and the gut lies 

 in contact with the testis. Though this form of hernia is termed complete congenital, the term 



Complete oblique inguinal 



Complete congenital 



Incomplete congenital 

 FIG. 1084. Varieties of oblique inguinal hernia. 



