Benefits and Dangers of in-and-in-breeding 159 



While in-and-in-breeding serves a most useful 

 purpose, under certain conditions, it should not be 

 forgotten that it may also cause deterioration in 

 various ways. A commonly accepted belief is, that 

 the practice of in-and-in-breeding may result in a 

 reduced constitution, may weaken the mental vigor, 

 reduce the size of the individuals and make them 

 less prolific. Many instances might be cited to show 

 that any one or all of these evils may accrue from 

 in-and-in-breeding, and it is also true that any one 

 or all of these evils will not be produced to a cer- 

 tainty by this practice. 



It is recognized that both good and evil results 

 may follow the practice of in-breeding, but it is 

 not generally accepted that the good or evil results 

 are in proportion to the degree of relationship 

 between the animals mated. If in-breeding is to be 

 practised, the degree of relationship should not be 

 the determining factor. A more rational selection 

 is based on the individual merits of the animals to be 

 mated. When related individuals are to be bred 

 together, the selection should be made on the suita- 

 bility of the animals to each other and not wholly 

 on the degree of relationship. 



The safety with which in-and-in-breeding may 

 be practised will depend largely on the skill that 

 is used in selecting the related animals that are 

 to be mated, and on the extent to which the practice 

 is carried. The skilful breeder will be able to derive 



