226 A STUDY OF HEREDITY IN INSANITY [Oct. 



basis of the information obtained by questioning the relatives, 

 neuropathic states from the normal state and in the case of a 

 neuropathic state to identify, if possible, the special variety. Such 

 diagnosis often enough presents great difficulty when there is 

 opportunity for direct observation, but when it has to be based 

 upon observations of untrained informants related from memory 

 the difficulty is, of course, greatly increased and with it the chance 

 of error. We have endeavored to reduce the amount of error 

 from this source by interviewing personally as many as possible 

 of the nearest relatives of the patients whose pedigrees were 

 being investigated, and by the practice of tracing almost all the 

 families not farther than to the generation of grandparents, for 

 the farther back our inquiries extended the more scant and more 

 vague was the information which we were able to obtain. 



To the difficulty of diagnosis is added the further difficulty 

 which results from the impossibility in the present state of psy- 

 chiatry of precisely delimiting the conception of the neuropathic 

 constitution. To this matter we shall have occasion to revert in 

 subsequent sections. 



In the analysis of data it was often necessary in the case of a 

 normal subject to determine whether the case was one of duplex 

 or of simplex inheritance, it having appeared early in the course 

 of our study that the normal condition was dominant over the 

 neuropathic condition. The fact of simplex inheritance we were 

 able in some cases to establish on the basis of the existence of 

 neuropathic manifestations in the ancestors or collateral relatives 

 of the subject; in other cases this evidence was lacking as our 

 information did not extend to the more remote generations, so 

 that it was necessary to assume the fact of simplex inheritance 

 on the basis of the existence of neuropathic offspring: the two 

 types of material have been treated separately. On the other 

 hand, the fact of duplex inheritance was in every case based upon 

 the absence of neuropathic manifestations in ancestors and col- 

 lateral relatives, as far as known, as well as in the offspring; — 

 but inasmuch as in scarcely any case was the family history traced 

 farther back than the third generation it is clear that the possi- 

 bility of simplex inheritance was in no case positively excluded; 

 we have here, therefore, another source of error which, fortu- 

 nately, is slight, and affects the least important part of our mate- 



