132 The Third and Fourth Generation 



among our immigrants in order to refuse them 

 admission to this country. 



See what a single unfortunate aUiance can 

 produce. A young man to whom Goddard 

 gives the fictitious name of Martin Kallikak 

 had children by a feeble-minded girl in the days 

 before the CivU War. There have been traced 

 some 480 descendants from this mating, and all 

 of them are below normal intelligence. Later 

 this same man married a good Quaker girl, and 

 496 of the descendants of this marriage have 

 been traced, all of normal mentality. The 

 contrast is strikingly instructive, for the con- 

 ditions are almost those demanded by a 

 scientific demonstration. 



Such cases as those cited are interesting 

 from the standpoint of the student of heredity. 

 They are tremendously significant to the 

 average citizen because there is in the United 

 States a very large feeble-minded population, 

 estimated at 200,000, nine-tenths of whom are 

 at large, free to reproduce their kind, and very 

 prone to interbreed, because the feeble-minded 

 are seldom sought as legitimate mates by persons 



