128 The Thied and Fourth Generation 



to show the heritability of this defect and its 

 relation to alcoholism, insanity, syphilis, etc. 

 Briefly, syphilitic infection is a fairly common 

 cause of feeble-mindedness in children. There 

 is a higher percentage of feeble-mindedness in 

 the offspring of alcoholic parents than among 

 those of parents not addicted to it. There 

 seems little or no causal relation between 

 feeble-mindedness and insanity. But aside 

 from feeble-mindedness that may be produced 

 by such causes or by occasional accidents such 

 as falls, blows on the head, there is the great 

 mass of feeble-mindedness that is wholly a 

 matter of heredity. 



If a feeble-minded individual comes from 

 parents both of whom are congenitally feeble- 

 minded or who both have a great deal of feeble- 

 mindedness in their ancestry, such a one is taken 

 to be a pure recessive as far as this character is 

 concerned, and his germ cells have a double 

 dose of the factor for feeble-mindedness (FF). 

 When two such persons mate, their offspring 

 would be expected to be aU feeble-minded, for 

 aU eggs and sperm contain the factor F, and 



