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4 * 8 PA THOGBNIC BA CTERIA.
interlobular veins. The kidneys are acutely inflamed
and the urine is albuminous. The heart-muscle is
spotted, gray, and fatty. In the intestinal tract the pic-
ture of the disease will be found to vary according to its
The contents of the small intestine are yellowish,
watery, and mucous; Peyer's glands are enlarged. In
the neighborhood of the pylorus, ecchymoses and exten-
sive extravasations of blood are common. The bacilli
are found in all of the organs.
The house mouse is very susceptible to the disease;
guinea-pigs much less so, -fa c.cm. of a-virulent cul-
ture often being required to kill them. Pigeons are still
more refractory, and Smith found that ^ c.cm. of a
bouillon culture injected into the breast-muscles' was
required to kill them.
In spite of the fact that hog-cholera is a disease of
swine, and that it is from dead swine that the bacilli are
obtained, these animals are not very easily affected arti-
ficially. They snow no symptoms when injected subcu-
taneously, but almost invariably die after intravenous
injection of 1-2 c.cm. of a virulent culture.
Smith found that feeding with 200-300 c.cm. of a
bouillon culture after a day's fasting, or with small quan-
tities administered daily, would also cause death, with a
widespread diphtheritic inflammation of the stomach and
colon. Feeding with the organs of dead hogs produces
the same lesions as the administration of the culture.
As early as 1886 Salmon and Smith found it possible
.to produce, in both very and partly susceptible animals,
immunity to hog-cholera by gradually accustoming them
to increasing doses of the bacteria. DeSchweinitz iso-
lated from cultures of the bacteria two toxic substances,
a ptomain (sucholo-toxin) and an albumose (sucholo-albu-
min), together with cadaverin and methylamin. With
these substances he seems to have been able to produce
immunity. Selander and Metschnikoff found that im-
munity could be produced more quickly by the use of