MIRACLES' OF SCIENCE 



ed, when the parents were first or second cousins, 

 the proportion of deaf offspring was 34.6 per cent. ; 

 and in one case in which the marriage partners were 

 nephew and aunt, 75 per cent, of the children were 

 deaf. 



Of similar import are the facts regarding the in- 

 heritance of the condition that leads to mental over- 

 throw. Of course insanity as such is not heritable, 

 but the instability of the nervous system that makes 

 one liable to mental overthrow is very pronouncedly 

 heritable. Doctors Cannon and Rosanoff have made 

 careful investigations of the families of patients at the 

 King's Park State Hospital for the Insane. Omit- 

 ting a certain class of "organic" cases, they found in 

 all the cases recorded that when both parents had 

 any form of insanity all of the children sooner or later 

 became insane. If one parent is insane and the other 

 normal but of insane stock, half of the children tend 

 to become insane. What is still more significant, per- 

 haps, from our present standpoint is the fact that 

 when both parents, though themselves normal, belong 

 to an insane stock, about one fourth of the children 

 becomes insane. Dr. H. H. Goddard in his studies 

 of the defective children at Vineland finds similar 

 facts regarding the heredity of the feeble minded. 



These are facts of the utmost practical importance. 

 Few other afflictions are more lamentable thaii men- 

 tal overthrow, and no rightminded person could con- 

 template with composure the thought of producing 

 offspring foredoomed to become insane. So no 

 person in whose family there is a strain of insanity, 

 near or remote, should contemplate matrimony with- 



206 



