170 PRINCIPLES OF STOCK-BREEDING. 



It has been supposed by some writers that, in 

 cases like the preceding, where high-bred animals do 

 not breed readily among themselves, a condition ex- 

 ists analogous to that observed in " self -impotent " 

 plants and other hermaphrodite organizations that are 

 incapable of self-fertilization. 1 The cases, however, in 

 which high-bred animals are perfectly prolific seem to 

 indicate that in-and-in breeding and fecundity are not 

 incompatible, and that the loss of fertility, when it 

 occurs in high-bred animals, is better accounted for 

 on the principle that, in the correlation of functions, 

 if one is greatly in excess, another may be obscured. 



As the impaired function of reproduction may fre- 

 quently be restored by a suitable selection of animals 

 within the limits of a high-bred family, it would like- 

 wise appear that the functional defect of the organiza- 

 tion is not a specific one resulting from an approxi- 

 mate identity in blood. 



From the well-known fact that high-bred animals, 

 when kept under different conditions are more prolific 

 than those that are treated in the same manner, 2 it 

 must be apparent that the suspension of the reproduc- 

 tive functions, in the cases under consideration, is pro- 

 duced by the modifying agencies to which the animals 

 are subjected, and not by close breeding. 



The infertility of some of the Booth family of 

 Short-Horns 8 has been attributed to the forcing sys- 



1 Darwin's "Animals and Plants under Domestication," vol. ii., p. 

 177. 



2 Sebright's "Art of improving the Breeds," etc., p. 16 ; "American 

 Cattle," by Allen, p. 206 ; Sinclair's " Code of Agriculture," p. 95. 



8 Carr's "History," p. 90. 



