Human Inheritance 203 viduals. The background of its expression appears to be connected in some way with the sex organs but what this connection may be is unknown, for it appears in both sexes which makes it difficult to account 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 physiological 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 established 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 [italics]defective[end italics] characteristics might be the ones, judging by analogy with mutant physical defects, that would be more likely to furnish evidence of Mendelian inheritance that 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 [end]