INHERITANCE OF MENTAL DEFECTS AND DISEASE 51 



parents is a neuropathic person (RR). On looking through the 

 charts I find that only three of the 19 cases fulfill this condition. 

 If one of the parents has a brother, sister or other near relative 

 who is neuropathic, the assumption that this parent is heterozy- 

 gous is only probable. In going over the charts for cases of this 

 kind I find a record in the alleged DRXRR matings of only five 

 instances. In all the other cases the conclusion is apparently 

 based on no evidence at all beyond the fact that it is necessary to 

 assume it in order to make the facts come out in accordance with 

 the hypothesis. 



The third class of cases discussed, the matings of a homozygous 

 normal with a double recessive, DD XRR is represented according 

 to the authors, by "five matings with a total of 18 offspring. 

 Theoretically all the offspring of such matings should be normal, 

 but capable of transmitting the neuropathic make-up to their 

 progeny. The charts show : 8 normal with neuropathic ofifspring, 

 7 normal with normal offspring, 2 normal without offspring, and 

 I died in childhood." The assumption that one parent is a 

 homozygous dominant is naturally somewhat unsafe. From the 

 nature of the case we can never know that this is correct, but 

 from what has just been quoted it may be inferred that this 

 assumption is made because all the children are normal, and some 

 of the grandchildren neuropathic. Of course some of these cases 

 cited may have been DRXRR matings which happened to have 

 only normal (DR) children. What the authors have done is to 

 divide up the cases in which normal and neuropathic mate into 

 DD X RR and DR X RR in such a way as to best make the results 

 fall into line with the theoretical expectations. That other 

 interpretations are not improbable is evident from what has 

 previously been said. 



The alleged DRXDR matings turn out more in accordance 

 with expectations since seven matings with 54 offspring yielded 

 12 neuropathic, and 34 normal individuals, and 8 who died in 

 childhood. 



A subsequent paper by Rosanoff and Orr deals in much the 

 same way with a larger amount of data, represented by 73 pedi- 



