272 BREEDING AND CROSSING. 



increased in their offspring in a double ratio. But on the 

 contrary, if a man unites with a woman of a different family 

 and a different predisposition, the idiosyncracy of the off- 

 spring to the diseases of either parent is likely to be pre- 

 vented or retarded. 



" With animals the case is different. If due attention be 

 paid, a principal object will be to breed from healthy sub- 

 jects, by which means one fertile cause of hereditary pre- 

 disposition to disease is prevented. A healthy form and 

 sound constitution are essential to successful breeding, and 

 for the development of those points we seek to obtain. 

 Thus the principal objection to breeding from near affinities 

 which exists in the human subject, does not obtain amongst 

 animals ; and even if, in the former, mental disease is more 

 apt to occur when this practice is pursued, this also is an 

 objection which does not apply to animals, though it has 

 been urged by some that sheep bred in and in are more sub- 

 ject to diseases of the brain — a conclusion, however, which 

 I am much disposed to doubt. 



" Thus the objections to breeding in and in are not insuper- 

 able ; what, however, are its advantages ? The stronger 

 resemblance there is in the qualities of both parents, sup- 

 posing those qualities are good, the more likely is it that the 

 offspring will be perfect. By breeding with a view to im- 

 provement, the greatest excellences are likely to be con- 

 centrated in one family ; if, therefore, the members of this 

 family were not coupled, they must probably be united to 

 inferior animals of either sex, by which practice improve- 

 ment will be materially retarded. It is, therefore, very fre- 

 quently the surest method of arriving at the greatest degree 

 of excellency, and thus it is a practice which has been fol- 

 lowed by the most eminent breeders of sheep with the 

 greatest success ; yet it does not possess any advantages 

 peculiar to itself and different from those we have stated, 

 and if two rams were obtainable possessing precisely equal 

 qualifications, I should not be disposed to select one because 

 he was a near relation to the ewe, but the contrary. 



'' In-and-in breeding may thus be either productive of good 

 or bad effects, but in neither case is the result to be attributed 

 to the close affmity, but rather to the circumstances con- 

 nected with it. If no care is employed either in selecting 

 or culling the flock, unquestionably both disease and defect 

 will arise ; and two animals, each predisposed to the same 



