40 CLINICAL APPLIED ANATOMY. 



often found at the termination of the small bowel, and a similar 

 explanation holds for the extensive involvement of the caecum 

 in some cases. Owing to the longitudinal axis of the ulcers, 

 stricture rarely results as a sequel of typhoid ulceration. 



The fact that the lymphoid aggregations of the bowel have their 

 bases set in large lymph sinuses accounts for the readiness with 

 which the mesenteric glands and retroperitoneal glands become 

 swollen during the progress of the disease. 



The lower part of the ileum is the common site of perforation 

 in typhoid fever. The richness of the lymphoid collections, the 

 free mobility, and the peristalsis necessary to overcome the 

 resistance of the ileo-caecal valve, sufficiently explain the 

 frequency of perforation here. The large bowel has thicker 

 coats, less lymphoid tissue, and is less likely to be ulcerated ; 

 consequently perforation is uncommon. Although the accident 

 has been known to occur in the ascending and in the transverse 

 colon, yet it appears to have been found more frequently in 

 the pelvic segment. This portion of the colon has a full 

 mesentery, is constantly varying in position with alterations in 

 distension of the urinary bladder, and is in close proximity to 

 the sphincters guarding the anus. The conditions therefore are 

 similar to those which obtain at the lower part of the ileum. 



Haemorrhage from the bowel in typhoid fever is usually the 

 result of the erosion of small vessels derived from the terminal 

 branches of the superior mesenteric artery. The terminal 

 arteries of the small bowel encircle the gut, reaching the bowel 

 in the mesentery ; at first they run for a short distance imme- 

 diately beneath the serous coat, then they perforate the muscular 

 layers and run in a deeper plane. It is obvious then that ulcera- 

 tion of Peyer's patches will sooner open an arteriole than 

 would ulceration nearer the mesenteric border of the intestine. 



The specific organism readily gains access to the blood stream, 

 and thus not only becomes widely distributed in the body, having 

 been found in the gall bladder, bones and cerebral meninges, but 

 also produces special vascular lesions. Typhoid phlebitis with 

 thrombosis is the most important immediate lesion. Thrombosis 



