IN-BREEDING 239 



which are undersize, weak in constitution, or that show a 

 tendency to low fertility should not be in-bred. It is 

 not always possible to detect the presence of these tend- 

 encies in a single generation, hence a knowledge of family 

 history and pedigree is important. Given an animal 

 of unusual merit with strong constitution, good size and 

 strongly fertile, the breeder runs little risk in practicing 

 in-breeding for a limited time. 



222. The truth about in-breeding. In the midst of 

 such diversity of opinion as exists concerning the results 

 and value of in-breeding, the practical breeder may well 

 be puzzled. Sweeping generalizations either for or against 

 the practice are apparently unwise at this time. An 

 unreasoning prejudice against the practice will result in 

 withholding from breeders a valuable method of breed- 

 ing which has been in many cases the chief reliance of 

 the world's greatest improvers of the domestic animals. 

 On the other hand, a blind following of those enthusiasts 

 who have claimed for in-breeding some mysterious power 

 in the improvement of animal character will certainly 

 lead to disaster. 



The practice of in-breeding has been compared to a 

 powerful medicine which in the hands of a skillful physi- 

 cian may decide the issues of life, but in the hands of the 

 novice becomes a dangerous and often fatal instrument. 

 In-breeding may be practiced successfully, but only by 

 those who are familiar with the biological principles 

 involved, and who are familiar with the results which 

 sometimes follow the mating of nearly related animals and, 

 what is quite as important, who know the ancestral his- 

 tory of their breeding stock. 



Whether we accept the view that evil is an incidental 

 result due to the intensification of undesirable qualities 



