32 PRINCIPLES OF BREEDING. 



if the possession of any good qualities can fully com- 

 pensate, it should be mated with one which excels in 

 every respect in which the other is deficient, and on no 

 account with one which is near of kin to it. 



Notwithstanding the importance due to the subject 

 of hereditary diseases, it is also true that few diseases 

 invariably owe their development to hereditary causes. 

 Even such as are usually hereditary are sometimes pro- 

 duced accidentally, (as of course there must be a begin- 

 ning to everything,) and in such case, they may, or may 

 not be, transmitted to their progeny. As before shown, 

 it is certain that they sometimes are, which is sufficient 

 reason to avoid such for breeding purposes. It is also 

 well known that, in the horse, for instance, certain forms 

 of limbs predispose to certain diseases, as bone spavin 

 is most commonly seen where there is a disproportion 

 in the size of the limb above and below the hock, and 

 others might be named of similar character ; in all such 

 cases the disease may be caused by an agency which 

 would be wholly inadequate in one of more perfect form, 

 but once existing, it is liable to be reproduced in the 

 offspring — all tending to show the great importance of 

 giving due heed in selecting breeding animals to all qual- 

 ities, both external and internal, so long as "like pro- 

 duces like." 



