THE LARGE INTESTINE. 



sphincter, and then ascending for an inch or two, in con- 

 nection with the mucous coat and its cellular structure, 

 into which they are inserted. This arrangement explains 

 the protrusion of the mucous coat in prolapsus ani. 



The mucous coat is thick and red, presenting at the upper 

 portion of the rectum rather a smooth surface, while at the 

 lower are seen longitudinal folds called columns, which 

 allow of the distension of this intestine, and also some 

 transverse folds which are not regular as to numher or 



FIG. 186. 



size. At the lower end of the columns, and between them, 

 pouches are observed, (Fig. 186.) A radiated wrinkling is 

 seen around the anus, which is formed by the contraction 

 of the external sphincter. The margin of the anus is sup- 

 plied with sebaceous follicles, and the whole mucous coat of 

 the rectum abounds with mucous follicles. 



The arteries of the large intestine are branches of 

 the superior and inferior mesenteric, and of the internal 

 pudic arteries. Its veins enter into the vena porta?. The 

 solar and hypogastric plexus of the sympathetic supply it 

 with nerves. 



FIG. 186 represents a Section of the Anus and Rectum, showing the rectal 

 pouches, a a Columns of the rectum, b b Rudiments of columns, c Inter- 

 nal sphincter divided, d External spincter divided. t e Folds of skin on the 

 Bates. / Pouches, g Brisiles in the pouches. 



