HUMAN INHERITANCE 203 



vidiials. The background of its expression appears 

 to be connected in some way with the sex organs but 

 what this connection may be is imknown, for it 

 appears in both sexes which makes it difficult to ac- 

 count for the disturbance on the basis of a sex 

 endocrine. 



At best one can say, perhaps, that in certain 

 strains and perhaps under certain conditions mental 

 disorders appear, but so long as neither the physio- 

 logical background of insanity, or the external 

 agents, that are contributory, are known, its genetic 

 relations must remain obscure. 



If these "best cases" are so far from being estab- 

 lished on a scientific footing, it is not particularly 

 profitable to discuss the many claims that have been 

 set up for other mental traits, even though it must 

 be conceded that defective characteristics might be 

 the ones, judging by analogy with mutant phys- 

 ical defects, that would be more likely to furnish evi- 

 dence of Mendelian inheritance than the less extreme 

 differences that distinguish "normal" individuals. 

 The important point, however, to be urged is that 

 the "mental traits" in man are those that are most 

 often the product of the environment which obscures 

 to a large extent their inheritance, or at least makes 

 very difficult their study. 



While the inheritance of disorders relative to 

 human behavior are of importance to the pathologist 

 and to the penologist, the inheritance of individual 



