SYMPTOMS AND LESIONS 55 



rhage. Ecchymoses more rarely visible. Ulcers, 

 apparently originating in these ecchymoses some- 

 times occur on throat and between forelegs. (In 

 hot weather purple discoloration appears a few 

 hours after death in hogs, especially fat ones, 

 dead from any cause.) 



The pathology and microscopic tissue changes 

 produced by hog cholera virus are not well worked 

 out, but nevertheless the relation between primary 

 filterable virus lesions and secondary changes due 

 to other causes is fairly well understood. Let us 

 consider, for instance, lesions of the digestive mu- 

 cosa. Congestion appears first. It will disap- 

 pear or terminate in hemorrhage. Following 

 hemorrhage, regenerative or degenerative pro- 

 cesses will occur. The degenerative processes 

 may result in destruction and excoriation of the 

 epithelial cells, leaving an unprotected surface in 

 contact with the intestinal contents. Individual 

 resistance and the bacterial flora of the intestine 

 will determine future developments. Regenera- 

 tion will rule, or secondary infection will take 

 place. If Bact. necrophorus is present in suffi- 

 cient numbers, necrotic enteritis will be produced. 

 If B. suipestifer exists in overpowering numbers, 

 the familiar " button ulcer " may develop. 



In the intestine, we find the primary lesions due 

 to the filterable virus most frequently in the cse- 



