240 THE BREEDING OF ANIMALS 



already existing in the germ-plasm of the parent stock, or 

 whether we hold that certain definite evils are a necessary 

 result of mating animals of near kin, we must admit that 

 in-breeding has often been practiced with great success 

 and no appreciable injury. It is, therefore, clearly appar- 

 ent that there are conditions which are neither unusual 

 nor extremely rare under which in-breeding can be prac- 

 ticed with the assurance of success. 



223. Fixing characters by in-breeding. In-breeding 

 has been a powerful means of fixing and perpetuating 

 valuable characteristics in the domestic animals. It is 

 still a valuable method to be employed for the same pur- 

 pose. But in-breeding is only a means to an end and not 

 the end. In-breeding possesses no magic or occult power 

 which will be exerted for the improvement of animals. 

 While it works powerfully in fixing the good qualities, 

 it is no less potent in firmly establishing undesirable 

 qualities which may be present in the parent stock. And 

 in this fact lies the chief danger from in-breeding. In 

 fixing the good characters, we may unconsciously 

 strengthen the powers of transmission in the direction 

 of bad qualities. The most skillful breeders are less 

 likely to err in the direction of perpetuating tendencies 

 to evil, and history gives ample confirmation of the cer- 

 tain good which does follow in-breeding when practiced 

 with intelligence by skillful and experienced breeders 

 and accompanied by rigorous selection. 



It has often happened in the experience of breeders that 

 a sudden mutation has appeared in a single animal. This 

 mutation may represent a high degree of improvement in a 

 certain character or characters which the breeder has 

 long sought to develop in his breeding stock. This 

 variation appears in one animal only. It is highly 



