lung tissue. Lung solidified, red. Pneumonia of

PLATE 2. Lung of pig showing ecchymoses due to acute hog cholera. These appear in greater numbers on the apical and cardiac lobes

plus Bact. suisepticum. Cephalic and cardiac lobes first to be affected, later other parts may solidify. Solidified portion usually red or reddish gray. Usually bronchopneumonia. Interlobular

spaces well defined macroscopically, due to infiltration of leucocytes or blood. Tendency toward necrotic and caseous masses in cases of longer standing. Pleuritis constant. Pleuræ often thickened, rough, white, adherent.

Pneumonia, characterized by necroses which start from various foci, tending to involve all structures alike, sometimes spreading to the heart by contiguity. Filterable virus plus Bact. necrophorus.

Pneumonia, often semichronic, tending toward formation of multiple abscesses visible beneath the pleura, as slightly raised, yellow areas. Visible on section in deeper parts. Pneumonic lung may be red. More often grayish in color. Due to filterable virus plus B. pyocyaneus.1

Heart. Usually normal. Filterable virus lesions consist of petechiæ and ecchymoses which are visible on the surfaces of the auricles, usually the left. Sometimes congestion of coronary vessels. Heart itself rarely the seat of secondary lesions. Epicarditis and pericarditis often result from secondary infection with Bact. suisepticum. Spleen. Sometimes normal or slightly enlarged. Very small bright-red protruding hem

1

1 Hog cholera virus is only one of several influences capable of producing primary changes which, in the presence of secondary invasion with either Bact. necrophorus or B. pyocyaneus may result in the lung lesions mentioned in connection with these organisms. For instance, we regard lung worms in combination with B. pyocyaneus as a frequent cause of pneumonia in pigs.

orrhages beneath capsule are normal. These are frequently on ventral surface near the hilus, not so often along the borders and on the dorsal surface. Characteristic filterable virus lesions consist of black, well defined slightly raised hemorrhages 1/4 to 2 centimeters in diameter, located practically always somewhere on the margin. Spleen may be enlarged, dark, friable, engorged with blood. Due usually to secondary invasion with B. suipestifer, sometimes to other causes. Not of much diagnostic value as related to hog cholera.

Liver. Macroscopic appearance usually normal. Very exceptionally ecchymoses, seemingly due to hog cholera virus, are visible beneath the capsule. Often shows degenerative changes, probably due to hog cholera virus, but by no means characteristic, as they may be due to a variety of

causes.

Kidney. Very rarely normal. Seat of the most characteristic and constant hog cholera lesions, consisting of petechiæ. Organ may be changed as follows:

Normal in color, capsule peels easily. Surface of kidney studded with petechia which appear beneath the capsule, involving the glomeruli as well as other parts. On section, the petechiæ are seen variously distributed in the cortex, in the medulla, and sometimes in the membrane of the