66 HOG CHOLERA 



ers have so enlarged and darkened the entire or- 

 gan as to render them invisible, and because post- 

 mortem changes take place rapidly. The enlarged, 

 dark, pulpy spleen which is often encountered in 

 hog cholera outbreaks is of little significance in 

 diagnosis, because it is so frequently the result of 

 other causes. 



The heart reveals no macroscopic lesions in the 

 vast majority of cases, but the petechiae which are 

 sometimes visible on the left auricle, less fre- 

 quently on the right, and rarely involve the ven- 

 tricles, are usually caused by hog cholera virus. 



The lungs are often normal. If the surfaces are 

 dotted with ecchymoses, the fact suggests hog 

 cholera quite strongly, but occasionally these le- 

 sions are due to other causes. 



The laryngeal mucosa is often the seat of pete- 

 chiae, which are characteristic of hog cholera. 



Examination of the intestinal mucosa often aids 

 in making a diagnosis, but the lesions encountered 

 are often difficult to interpret. Certain irritants 

 cause changes which may be confused with those 

 due to hog cholera, and secondary invasion tends 

 rapidly to modify filterable virus lesions so that 

 they are difficult to identify. Ecchymoses and 

 larger hemorrhages, as well as ulcers of recent 

 origin, when distributed near the ileocecal valve 

 and elsewhere in the mucosa of the caecum and 

 upper colon, may be accepted as supplementary 



