ANATOMICAL AND PI 1 VSIULUCilCAL rACTOKS 79 



other ring oi" lymphoid tissue near the ileocecal valve. Lymplioid 

 tissue is scattered along- the mucoiLs membrane of the entire intes- 

 tinal ti-act, but opposite tlie attachment of the mesentery and at 

 the lower end of the ileum arc rather extensive areas of it calh^d 

 •'Peyer's patches." Peyer's patches are commonly the site of ex- 

 tensive ulceration in typlioid fever and in intestinal tuberculosis 

 as well as in ileocolitis. Ik'Iow the ileocecal valve is a lymphoid 

 vestigial oi-gan, the vermiform appendix. 



Ulceration of Intestixe. — In some cases of tularcmui, (((frfuudo- 

 cytic anc/hta. and in melioidosis, there occurs extensive ulceration 

 of the entire alimentary canal. Davis (1928) has reviewed his 

 own work and that of others on the lymphatics of the respiratory 

 and intestinal ti-act. He observed extensive infiltration of plasma 

 cells in the upper respiratory mucous membrane under the epi- 

 thelium of the crypts and along strands of connective tissue. In- 

 filtrations of similar cells were observed by Aschoff in his studies 

 of the appendix. Davis seems to feel that these plasma cells are 

 indicative of either chronic or at least frequent inflannnation. 

 CTOodpasture's (1937) work suggests that the young plasma cell 

 may function as a host cell for certain bacteria. 



The walls of the intestine may become infected directly through 

 the mucous membrane by specific pathogenic organisms such as 

 E. typhosa or the tubercle bacillus, or the infection may be due 

 to the pyogenic organisms present, and the portal of entry may 

 be through erosions from various causes as suggested by Ivy (1920, 

 1925). The infections may be hematogenous or lympliogenous in 

 origin. Malignancy also is responsible for secondary infections. 

 Direct extension from an abscess existing in some organ or mass 

 to whicli the intestine has become attached by inflammatory adhe- 

 sions may lead to invasion from the peritoneal side. 



Ulcer, Pancreatitis, Cholecystitis. — The anatomical relation- 

 ships near the pylorus of the stomach are quite important since 

 ulcer commonly involves the cap or the walls of the duodenum just 

 below the ca]\ The presence of ulcer interferes with the normal 

 functioning of tlie gastrointestinal tract in various ways, is a source 

 of mild or severe hemorrhage and is a defect in the intestinal wall 

 that may lead to perforation and peritonitis. It should be remem- 

 bered that the secretions from the liver and pancreas enter the duo- 

 denum as a rule through the ampulla of Vater. A stone lodging in 



