22 



Farmers 9 Bulletin H67. 



subjection by not inbreeding, we double the chance of its appearing 

 when we do inbreed. It seems possible to inbreed some animals 

 much more intensely than others, and certain strains of breeds in 

 the same species exhibit similar traits. To cite specific instances, 

 cattle which have a special susceptibility to tuberculosis, horses with 

 a tendency to certain unsoundness, such as roaring or spavin, should 

 not be inbred. The safe rule, therefore, is not to mate closely re- 

 lated animals which have the same defects, either themselves or in 

 their immediate ancestors. 



Percheron Stallion, Dragon. 



FIG. 14. Descendant of a long line of impressive ancestors and himself a sire of 



valuable draft horses. 



Inbreeding should be practiced only by the most skillful breeders, 

 and by them only when they have definite knowledge of the an- 

 cestry. Judiciously used, inbreeding results in a rapid fixing of 

 type and enables the breeder to obtain results much more rapidly 

 than without its use. It is like any other high-powered implement. 

 Properly used, it is a wonderful adjunct to human efforts; in the 

 hands of the ignorant and careless it is a source of danger. 



