HUMAN INHERITANCE 201 



determined to what extent feeble-mindedness is due 

 to syphilis, it is extravagant to pretend to claim that 

 there is a single JNIendelian factor for this condition. 



Family pedigrees in which an unusual number of 

 individuals below par are present undoubtedly give 

 the impression that something is inherited, but until 

 all the social conditions surrounding the childhood 

 of the individual are examined and given proper 

 weight, serious doubts will arise as to what form of 

 inheritance is producing the results. It is quite prob- 

 able that there are extraneous factors involved in 

 such pedigrees. 



There is no a priori objection to the assumption 

 that different sense organs and different brains react 

 as differently as do other organs of the l)ody. Those 

 that react below some selected standard might be 

 called feeble-minded; but there are no grounds for 

 assuming that the results are due to one particular 

 defect in the nervous system, and in fact a critical 

 study of the cases shows that they are probably not 

 all due to a single factor difference or even to the 

 same ones. The pedigrees that have been published 

 showing a long history of social misconduct, crime, 

 alcoholism, debaucherv, and venereal diseases are 

 open to the same criticism from a genetic point of 

 view^; for it is obvious that these grouj^s of individ- 

 uals have lived under demoralizing social conditions 

 that might swamp a family of average persons. It 

 is not surprising that, once begun from wliatever 



