HUMAN HEREDITY AS REVEALED BY PEDIGREES 459 



We must, therefore, take all genetic studies of feeble-mindcdness with 

 a grain of salt. 



H. H. Goddard, probably the most distinguished of the students of 

 feeble-mindedness, has studied many pedigrees and compiled statistics 

 concerning 300 of the best of these. Of the cases of feeble-mindedness 

 diagnosed as such by him, 164 (54 per cent) are considered unquestion- 

 ably hereditary, 71 (23 per cent) probably hereditary, and the rest 

 probably non-hereditary. Goddard seems to be convinced that feeble- 

 mindedness is due to a single recessive gene. He cites 42 cases in 

 which heterozygous, phenotypically normal, mothers (NF), when 

 mated with feeble-minded fathers (FF) produced 71 feeble-minded 

 and 73 normal offspring out of a total of 144. This is almost too close 

 an approximation to the expected Mendelian ratio of 1 to 1. From 

 26 matings of apparently heterozygous fathers and mothers (presum- 

 ably NF) there were produced 122 known children, 83 of whom were 

 normal and 39 feeble-minded, suggesting the expected Mendelian ratio 

 of 3 to 1. Of 476 children of parents both of whom were feeble-minded 

 (FF),only 6 were normal in intelligence, and thes? are suspected of being 

 illegitimate. In Figures 86 and 87 are presented two typical pedigrees 

 of feeble-minded families studied by Goddard. The first of these pedi- 

 grees (Fig. 86) shows the dire effects resulting from the interbreeding of 

 feeble-minded parents. The children are all feeble-minded except the 

 considerable number that died in infancy, presumably because of 

 neglect and ignorance of the parents. The second pedigree (Fig. 87) 

 illustrates what approximates a controlled scientific experiment, for 

 one woman was married twice, once to a normal man and once to a 

 feeble-minded man, and had several children by each. All of the off- 

 spring from the normal father are normal (but evidently heterozy- 

 gotes), while all those of the feeble-minded father were feeble-minded 

 and otherwise abnormal. 



It is interesting to note that a very large proportion of juvenile 

 criminals and prostitutes, when given the Binet test, rank as feeble- 

 minded. Tests of juvenile criminals in various states show the fol- 

 lowing facts : In New Jersey 46 per cent of juvenile criminals are feeble- 

 minded; in Ohio, 70 per cent; in Virginia, 79 per cent; and in Illinois, 

 89 per cent. It would seem to be a conservative estimate that fully 

 half of juvenile criminals are feeble-minded. 



It has also been showm that the great majority of prostitutes and 

 girls who have been placed in reformatories for sex-delinquency are 

 feeble-minded. Tests of large numbers of girls in an Illinois reforma- 



