182 THE BREEDING OF ANIMALS 



to the nature of immunity, but undoubtedly the known 

 immunity of certain individuals or families to certain 

 diseases may become the basis of important future im- 

 provements in the domestic animals. In recent years 

 it has been found that certain hogs are immune from hog 

 cholera. Experiments have been suggested to deter- 

 mine whether or not it would be possible to develop a 

 race of swine immune to this dreaded disease. 



It is possible for animals to acquire immunity through 

 vaccination of actual infection of the disease itself. Such 

 immunity is not transmitted. It is doubtful whether 

 there exists any congenital immunity, but investiga- 

 tions along this line might be fruitful of results. 



