THE CROSSING, &C, OF CATTLE, ET AL. 307 



rate animals.' We thus see that there has been ex- 

 tremely close-interbreeding with Shorthorns ; but Na- 

 thusius, after the most careful study of their pedi- 

 grees, says that he can find no instance of a breeder, 

 who has strictly followed this practice, during his 

 whole life. From this study, and his own experience, 

 he concludes that close-interbreeding is necessary to 

 ennoble the stock; but that, in effecting this, the great- 

 est care is necessary on account of the tendency to in- 

 fertility and weakness." 



Had the defect, which the name, Shorthorns, con- 

 notes, been supplied, the animals just mentioned, could 

 go on interbreeding, for double, treble the time ; aye, ' 

 forever, were there no positive differences, possessed 

 by other cattle, — thereby implying that, in some details, 

 the former were deficient. The evil, of the shortened 

 horns, is indirectly, but surely shown, by the following 

 remark of Darwin: 



"It may be added" (p. 174, Vol. ii, Animals and 

 Plants, &c), "that another high authority asserts, that 

 many more calves are born cripples, from Shorthorns, 

 than from any other and less closely interbred races of 

 Cattle." 



This effect is due, to the fact, that the horns and the 

 legs are correlated, in all animals ; and, therefore, when 

 one, of two parts which are so tied or correlated to- 

 gether, is absent or reduced, the other is, in some 

 degree, weakened. This injury to the balance of the 

 organization, is, of course, augmented by the mating 

 of two individuals in which the said defects similarly 

 obtain ; and, this is the reason of the strange phenome- 

 non which Darwin notes. 



