SYMPTOMS AND LESIONS 43 



moment neglected discussion of less characteris- 

 tic changes which frequently take place. If we 

 consider each organ separately, extending our ob- 

 servations to include less characteristic changes, 

 as well as those produced by secondary invaders 

 discussed in a previous chapter, a more complete 

 picture, and a more accurate interpretation 1 of the 

 pathological anatomy encountered in field cases 

 can be presented. 



Mouth and pharynx. Mucosa usually normal. 

 Hog cholera virus may be primary cause of ulcers. 

 These are sometimes present in hog cholera out- 

 breaks, and appear as dark brown necrotic patches 

 on gums, lips, tongue and other parts. Probably 

 due to primary injuries caused by the filterable 

 virus, and certainly caused by B. necrophorus as 

 a secondary invader. B. necrophorus ulcers oc- 

 cur independent of filterable virus infection. 



Stomach. Mucosa frequently normal. Filter- 

 able virus causes petechise, ecchymoses or larger 

 suffusions in fundus. Congestion due to the same 

 cause usually present. Ulceration relatively rare, 



1 We are fully aware that with our present knowledge such an 

 interpretation can be only approximately correct, but nevertheless 

 there are certain well-defined tendencies which should be indicated. 

 Our conception of the primary filterable virus lesion has been 

 gained, during the last ten years, by performing autopsies on 

 hundreds of pigs which were killed about a week subsequent to 

 injection with virus. The virus was obtained from several sources 

 in various states, some was filtered, some was not. We have also 

 investigated several of the secondary invaders, and the combined 

 results of these investigations with those of similar nature con- 

 ducted by other workers, are reflected in the remarks which follow. 



