THE BREEDING OF MEN 



Mendel spoke of tallness as " dominant " in the 

 case of the pea and of shortness as " recessive, " 

 and these terms are so convenient that they have 

 passed into current usage. The essential thing is 

 that the recessive trait, if its elements are present 

 in the germ-plasm of an individual, will inevitably 

 reappear in a percentage of the offspring of that 

 individual under certain conditions; and it has 

 been found that this fact is highly important from 

 the human standpoint, inasmuch as there are cer- 

 tain human traits that show the phenomena of 

 dominance and recessiveness in inheritance. 



This is particularly true, for example, with 

 defects of the brain and nervous system which 

 may manifest themselves in subnormal mentality. 



There is a growing body of evidence to show 

 that mental normality is dominant to mental ab- 

 normality, in the Mendelian sense of the word. 

 Hence, when a perfectly normal individual is 

 mated with one of subnormal mentality, the off- 

 spring will probably be normal ; but these normal 

 offspring, carrying the mental defect as a reces- 

 sive trait, if mated with other individuals of simi- 

 lar heritage, may have progeny about one-quarter 

 of whom are of defective mentality. 



As an illustrative example, I may cite a case 

 that came very recently under my observation. I 

 was asked to examine a boy of ten who was ob- 

 viously abnormal, and who on examination proved 

 to be feeble-minded. His parents were not only 

 normal mentally, but were both persons of excep- 

 tional ability, the father being a professor in a 



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