MORBID ANATOMY 257 



edge of the border where the slough begins. The latter may 

 have been parti}' shed, leaving a smooth line bounding the 

 cicatricial tissue. The submucous infiltration gradually disap- 

 pears toward the periphery of the ulcer and slightly outside of 

 the ulcer no inflammation of the membrane exists. Giant cells 

 have been observed in the intertubular tissues at the edge of 

 the ulcer. The depth to which the infiltration extends is not 

 always limited to the submucosa ; it may extend into the 

 muscular coats and cause inflammatory thickening and in- 

 flammation and the formation of new vessels in the subjacent 

 serosa. 



In some cases the necrosis, instead of appearing in circum- 

 scribed ulcers from one-sixteenth to one-half inch or more 

 across, involves the whole surface of the mucous membrane, 

 giving it the appearance of a so-called diphtheritic membrane. 

 In such cases the walls of the intestine are very much thick- 

 ened and so friable as to be easily torn with the forceps in 

 handling them. Such necroses are rare in epizootic cases, but 

 they frequently appear in animals which have been fed with 

 pure cultures of hog-cholera bacilli. 



The distribution of the ulcers varies but slightly. Thej^ 

 appear most frequently in the cecum and on the ileo-cecal 

 valve, as well as in the upper half of the colon. The lower 

 half is implicated in severe cases only and then less extensively. 

 The rectum is rarely ulcerated. The lower portion of the 

 ileum is ulcerated in a small percentage of animals, especially 

 when they have been fed with hog cholera viscera or cultures. 

 The stomach is occasionally the seat of slight ulceration. 

 The lymphatic glands of the affected intestine are usually 

 much enlarged, pale, tough and whitish on sections. The 

 spleen is rarely enlarged. The liver shows degenerative 

 changes. The heart and lungs are usually normal. The 

 broncho-pneumonia frequently found in young pigs in the 

 winter months must be ascribed primaril\- to exposure rather 

 than to the presence of hog cholera. 



In some outbreaks the acute and the chronic t3'pes are 

 not so clearly separated as indicated in the foregoing pages. 



