SYMPTOMS AND LESIONS 47 



spaces well defined macroscopically, due to infil- 

 tration of leucocytes or blood. Tendency toward 

 necrotic and caseous masses in cases of longer 

 standing. Pleuritis constant. Pleurae 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. necro- 

 phorus. 



Pneumonia, often semichronic, tending toward 

 formation of multiple abscesses visible beneath 

 the pleura, as slightly raised, yellow areas. Visi- 

 ble on section in deeper parts. Pneumonic lung 

 may be red. More often grayish in color. Due 

 to filterable virus plus B. pyocyaneus* 



Heart. Usually normal. Filterable virus le- 

 sions consist of petechiae and ecchymoses which 

 are visible on the surfaces of the auricles, usually 

 the left. Sometimes congestion of coronary ves- 

 sels. Heart itself rarely the seat of secondary le- 

 sions. Epicarditis and pericarditis often result 

 from secondary infection with Bact. suisepticum. 



Spleen. Sometimes normal or slightly en- 

 larged. Very small bright-red protruding hem- 



a 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 re- 

 sult in the lung lesions mentioned in connection with these organ- 

 isms. For instance, we regard lung worms in combination with 

 B. pyocyaneus as a frequent cause of pneumonia in pigs. 



