126 CATTLE-BREEDING. 



prolonged life and period of production, im- 

 proved flesh and milk-making powers, and often 

 highly-marked prepotency. 



A recent writer on the theory of breeding 

 says, in summarizing his remarks on this sub- 

 ject : "There is no one point on which practical 

 breeders, as well as scientists, are more per- 

 fectly agreed than that the ultimate tendency 

 of breeding in-and-in is injurious ; that when 

 carried to excess it will always result in a loss 

 of constitutional vigor in the produce ; that 

 while its tendency may be in the direction of 

 fineness of texture, lightness of bone, smooth- 

 ness, evenness, and polish, it is invariably at 

 the expense of robustness, strength, vigor, and 

 power. On the other hand, scientists, as well 

 as practical breeders, with perhaps equal unan- 

 imity concur in the belief that a cross in the 

 blood usually gives increased size and vigor to 

 the produce, and that cross-breeding, or pair- 

 ing of animals of distant varieties, usually re- 

 sults in increased fertility." 



Mr. Darwin is very decided in his view that 

 crosses of unrelated blood are in themselves of 

 high value. He says, for example : "The gain 

 in constitutional vigor derived from an occa- 

 sional cross between individuals of the same 

 variety, but belonging to distinct families, has 

 not been so largely or so frequently discussed 

 as have the evil effects of too close interbreed- 



