132 MARRIAGE AND HEREDITY 



Where then does the truth lie ? A study of the 

 general principles of heredity solves this as it does 

 many other social problems. In theory consan- 

 guineous unions may be harmless enough ; practically 

 it is well to avoid them. We have seen that diseases 

 and other physical peculiarities run in the blood. If 

 a family could be pronounced absolutely perfect in 

 mind and body, the intermarriage of its members 

 would probably be an advantage. Eaisers of prize 

 stock have found the process of in-and-in breeding in 

 some cases to be distinctly beneficial. But what 

 family is perfect? We have all a constitutional 

 weakness of some sort, and heredity warns us that 

 when two persons having the same complaint marry 

 each other, the evil is intensified in their children. 

 Double heredity is notoriously disastrous, for ex- 

 ample, in cases of insanity, and by analogy we may 

 conclude that it is no less so in heart disease, con- 

 sumption, and other constitutional maladies. All 

 family characteristics, good or bad, are unquestionably 

 accentuated by consanguineous marriages. 



The harmlessness of such unions in certain cases 

 does not imply their harmlessness in all; cousins 

 who are fond of each other can never be certain that 

 their marriage will not foster some latent family im- 



