158 HEREDITY AND EUGENICS 



A mental disorder which appears to be confined to 

 Russian Jews (see Davenport, 1920) is amaurotic 

 famil}^ idioc}', which runs in famihes and appears to 

 be a simple Mendelian recessive. Myoclonic epilepsy 

 (see p. 108) has been shown by the extensive pedigrees 

 compiled by Lundborg in Sweden to be inherited 

 in the same wa}'. It is recognised that epilepsy occurs 

 in a great variety of forms, and the pedigrees studied 

 by Davenport and Weeks and others indicate that 

 the common form at any rate follows the same rule 

 of inheritance. A relation between epilepsy and 

 feeblemindedness is also indicated, such that if one 

 parent is epileptic and the other feebleminded, all 

 the children will be either epileptic or feebleminded. 

 Various investigations indicate (Davenport, 1920) that 

 dementia praecox* maybe also a Mendelian recessive. 

 According to F. W. Mott {Proc. Roy. Soc. Med., June, 

 1920), this condition is accompanied by a complete 

 arrest of spermatogenesis. Riidin (191 6) finds that 

 various other psychoses accompany dementia praecox, 

 and thinks that a Mendelian explanation is possible. 

 Hoffman (1921), in a stud}'^ of dementia praecox and 

 the manic depressive condition, concludes that two 

 factors are involved in the former, while in the latter 

 a dominant character in some form is concerned. 

 Siemens (1921) gives a list of inherited abnormal 

 physical and psychical conditions. 



The appalling frequency of feeblemindedness in 

 some parts of America is to be seen from statistics 

 collected (Sessions, 191 7) in one county in Ohio, 

 where the feebleminded number i per cent, of the 

 population. An equal frequenc}^ throughout the 

 State of Ohio would mean 47,000 feebleminded within 

 its borders. The rapidity with which the problem 

 is becoming still more serious is to be seen from the 



* Adolescent insanity marked by melancholia and other 

 emotional states. 



