528 IOWA DEPARTMENT OP AGRICULTURE 



Q. Do you find that hogs are attacked with more violence 

 where there has not been any immunity in the herd for a num- 

 ber of years ? 



Dr. Niles: If hogs have been bred continuously on a certain 

 farm, without any animals having been brought in that have l)een 

 through cholera, I think you are apt to find that you develop a 

 type of hogs more susceptible to cholera than otherwise. If 

 cholera has ravaged a neighborhood for several years, you are 

 more apt to develop a type of hogs that is immune. 



