188 PRINCIPLES OF STOCK-BREEDING. 



cases occurring in the British Isles the condition is 

 acquired and not congenital. 1 



Of fifteen hundred and fifty-seven patients in the 

 insane asylums of Paris, Auguste Yoisin found none 

 that were the result of consanguinity. 3 



The facts that have thus far been collected in re- 

 gard to this subject seem to warrant the conclusion 

 that close breeding, in itself considered, is not injuri- 

 ous ; but, as it tends to fix and perpetuate the consti- 

 tutional defects that have been produced by other 

 well-known agencies, it should not be practised by 

 careless or inexperienced persons, who do not make a 

 judicious selection of their breeding-stock, as they are 

 likely to obtain, through its influence, the most un- 

 satisfactory results. 



(The most obvious objection to close breeding and 

 it is perhaps the only one of importance is the diffi- 

 culty of selecting animals that are free from constitu- 

 tional defects, and the danger arising from the ten- 

 dency of such defects to become dominant in the off- 

 spring. \ 



It must, however, be admitted that it is an impor- 

 tant means of improvement when judiciously prac- 

 tised, and that it constitutes the only known method 

 of securing an accumulation of the slight variations, 

 in a particular direction, that it may be desirable to 

 retain and perpetuate. 



The greatest improvement in the form and quali- 



1 Popular Science Monthly, June, 1872, p. 250. 



8 London Lancet, quoted in the Popular Science Monthly, Decem- 

 ber, 1873, p. 179; and in the Pacific Medical and Surgical Journal, 

 February, 1877, p. 408. 



