368 CLINICAL APPLIED ANATOMY. 



superior mesenteric chain. They communicate freely with the 

 lymphatics of the great omentum, and so come into relation with 

 the lymphatics of the lower border of the stomach. The lymphatics 

 of the ascending and descending colon also gain the superior 

 mesenteric chain. The glandular apparatus of the descending 

 colon is very poorly developed, which may account for the slow- 

 ness with which glandular infection occurs when the disease is in 

 the lower parts of the bowel. 



Malignant disease of the rectum is more common than in any 

 other part of the alimentary tract. It may either originate in 

 the glandular epithelium of the crypts of Lieberkiihn or in the 

 squamous epithelium of the anal canal. Squamous epithelium 

 extends up to the lower ends of the columns of Morgagni, and, 

 according to some authors, along these columns also. Local 

 extension of rectal growths is liable to involve important pelvic 

 structures, for the prostate, urinary bladder, vesiculae seminales, 

 and terminations of the vasa deferentia, lie in the closest contact 

 with the anterior rectal wall. In the female, the vagina and 

 uterus are apt to be invaded, and fistulous communications may 

 be thus established. By backward extension rectal growths 

 become adherent to the sacrum and coccyx. 



Ulceration of the Small Intestine. Tuberculous ulcers com- 

 mence in the Peyer's patches or the solitary follicles. These 

 ulcers tend to extend transversely round the bowel, following 

 the course of the lymphatic vessels. The lymphatic collecting 

 trunks in the mesentery sometimes become caseous, and can be 

 traced to the mesenteric glands, which may also be infected. 

 Since both the Peyer's patches and the solitary follicles are best 

 developed in the lower ileum, the ulcers are best marked in this 

 region. They are especially common just above the ileo-ca3cal 

 valve, owing to the obstruction offered by that structure to the 

 onward passage of the intestinal contents. 



Typhoid ulcers also originate in the lymphoid structures, and 

 are best marked in the lower part of the ileum. They are 

 produced by sloughing or necrosis of Peyer's patches and 

 follicles, and have not the same tendency to extend transversely 



