272 MARRIAGE AND DISEASE. 



on to their descendants, and not looking farther back, 

 the parents boldly assert that such a thing as insanity, 

 epilepsy, scrofula, &c., is unknown in their family. 

 They themselves have never been insane why, then, 

 should their children? In like manner children may 

 be epileptic, blind, mute, scrofulous, cancerous, cri- 

 minal, or deformed from direct inheritance, and yet 

 the family line be honestly declared to be healthy. 

 Hence the truth of Sir William Aitken's words : " A 

 family history including less than three generations 

 is useless, and may even be misleading." 



In consanguineous marriages, then, the danger 

 lies in the strong probability there is of both parents 

 bearing some particular taint of degeneration, which 

 will be deepened in their children, yet which might 

 be escaped if they each married a person not bearing 

 that same, or some allied, character. The blood 

 relationship in itself is innocent. It is the double 

 tendency to disease which brings about the evil to 

 the children. The marriage of two phthisical, or 

 scrofulous, or neurotic persons, whose families know 

 nothing of each other, would be equally pregnant 

 of evil with the marriage of cousins, or even nearer 

 blood relations similarly tainted. 



From the foregoing it is evident that the similarity 

 of temperament induced by a common environment, 

 and which I would call " social consanguinity/' must 

 be a potent factor in the production of all hereditary 

 degenerations. Living under similar customs, habits, 

 and surroundings, labouring at the same occupation, 



