Pathogenic Bacteria

HOG-CHOLERA. 415

yellowish to black. Occasionally these ulcers are slightly
depressed in outline. When cut across they are found to
consist of a firm, solid growth extending nearly through
the intestinal wall They are most frequent in the
cecum, upper half of the colon, and on the ileocecal
valve. In the chronic form of the disease the spleen is
rarely enlarged.

((In hog-cholera the first effect of the disease is
believed to be upon the intestines, with secondary inva-
sion of the lungs.'}

The most characteristic lesions of the disease are the
petechise and ecchymoses, the ulcerations of the large
intestine (Fig. 113), and the collapse and occasional bron-
chopneumonic changes in the lung.

The kidneys are nearly always affected, the urine con-
taining albumin and tube-casts.

The specific bacillus of hog-cholera was secured by
Sinifrh from the spleens of more than 500 hogs. It
occurs in all the organs and has also been cultivated
from the urine.

The organisms appear as short rods with rounded
ends, 1.2-1.5 p long and 0.6-0.7 // in breadth. They are
very actively motile. No spore-production has ever been
observed. In general the bacillus resembles in appearance
that of typhoid fever. It stains readily by the ordinary
methods, but not by Gram's method.

The bacilli possess numerous long flagella, easily
demonstrable by the usual methods of staining (Fig.
114).

No trouble is experienced in cultivating the bacilli,
which grow well in all the media.

Upon gelatin plates the colonies become visible in
twenty-four to forty-eight hours; the deeper ones spher-
ical with sharply defined borders. The surface is brown-
ish by reflected light, and is without markings. They
are rarely larger than 0.5 mm. in diameter and are homo-
geneous throughout. The superficial colonies have little
tendency to spread upon the gelatin. Their borders may