426 HOG CHOLERA 
of various kinds. Frequently the eggs of trichocephalus are imbedded 
in the slough. 
The extent of the submucous infiltration depends upon the age of 
the ulcer. In old ulcers it contains many newly-formed capillaries, 
and evidences of the formation of connective tissue are present. The 
capillaries may extend to the very edge of the border where the slough 
begins. The latter may have been partly shed, leaving a smooth 
line bounding the cicatricial tissue. The submucous infiltration 
gradually disappears 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 inflammation and the formation of 
new vessels in the subjacent serosa. 
In some cases the necrosis, instead of appearing in circumscribed 
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 thickened and so friable as to be easily torn 
with the forceps in handling them. Such necroses are rare in epizo- 
otic cholera, but they frequently appear in animals which have been 
fed with pure cultures of B. suipestifer. It is not clear, to what extent 
the ulceration and inflammatory conditions of the intestines are due 
to secondary infection. 
The distribution of the ulcers varies but slightly. They 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 viscera from infected 
hogs. The lymphatic glands of the affected intestine are usually 
much enlarged, pale, tough and whitish on section. 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 primarily 
to exposure rather than to the presence of hog cholera virus. 
In some outbreaks the acute and the chronic types are not clearly 
separated. Frequently recent hemorrhagic lesions seem to be 
