LESIONS IN ABDOMINAL CAVITY 137 



This valve is known as the ileocecal valve, and is of particular im- 

 portance in the postmortem examination of hog-cholera carcasses. 

 This valve derives its particular importance from the fact that 

 here is the most frequent source of the cholera ulcer. Ulcers ap- 

 pear at this point when they are not to be found in any other 

 part of the bowel. Just why this should be so is hard to explain, 

 but the fact remains that there is no other one location where the 

 button-like ulcer is so commonly found as on the ileocecal valve. 



Method of Ulcer Formation. — It is interesting to note just how 

 these ulcers form. In the normal bowel there are located beneath 

 the lining membrane little collections of lymphatic tissue, known as 

 lymph-follicles. These are of two kinds: viz., single or solitary 

 lymph-follicles — the so-called solitary foUicles — and larger patch- 

 like collections, consisting of several of these solitary follicles col- 

 lected together. These are known as the agminated follicles, or 

 better known as Peyer's patches. In the duodenum there are 

 found another group of lymph-glands known as Brunner's glands. 

 These, however, are rarely affected by the cholera virus. 



When the animal becomes infected by the virus of hog-cholera, 

 it appears that the germ has a special Hking for these lymphatic 

 glands in the walls of the intestine, and they burrow there and 

 enter the gland structure. It seems most probable that the 

 germs then multiply in the gland substance and thus increase in 

 number. By their presence and also, no doubt, by the action 

 of the_pgisons^ which they produce they set up an inflammatory 

 reaction in the gland substance. This results in an increase in the 

 number of gland cells. This increased number of gland cells 

 presses upon the small blood-vessels supplying the gland, and the 

 result is that the blood-supply is shut off. Any tissue or portion 

 of tissue shut off from its blood-supply soon must perish, and, as 

 a result, these tissues die. At the same time the enlargement 

 of the gland pushes the surface upward, and the dead tissue is 

 raised into the lumen of the bowel, giving the characteristic button- 

 like appearance. These ulcers are usually invaded by a second 

 germ, known as the necro-bacillus, which aids in the destruction of 

 tissue. 



In the course of a few days or weeks, if the animal is not de- 

 stroyed by the disease, the slough separates and there remains a 



