The fact of inheritance of the neuropathic constitution may be taken for granted. Much evidence has been adduced to prove that such inheritance occurs in accordance with Mendelian laws, but the subject is so complicated that more comprehensive studies must be made before we may consider the matter as settled. The application of skillfully devised measures of intelligence has shown us that there are many grades of intelligence between the idiot and the super-average. The so-called normals represent many types, the extremes of which are as far apart as the moron is from the low-grade normal. Recent studies of temperamental abnormalities have also revealed a wide variety of types and combinations. These abnormalities or marked peculiarities seem to be more or less dissociated from intellectual capacity. Children with super-average intelligence are frequently seclusive and morons often seem to be temperamentally normal. It becomes difficult, therefore, to establish standards of normality and to draw fixed lines between the normal and the neuropathic. This is especially true in studying family histories, when judgment must be based on reports of untrained observers. Mental disease may occur in a person of almost any type of intellectual or temperamental make-up. This fact was clearly demonstrated during the recent World War. Men of strong intellect and of exceptional poise who had withstood the strain of intense warfare for several months at last succumbed when weakened by wounds and deprivation of food and drink. These were extreme cases, but they illustrate the important principle that all men have limitations and may develop a psychosis or expire when their limit is reached. Psychopathic personalities give way to the common stresses of life, while stronger personalities yield only to extraordinary mental strain. It is evident, therefore, that the whole etiology of a case of mental disease must be carefully studied before the related family stock can be safely discredited. The data we have collected in the New York State Hospital Commission relative to the family history of patients seem to indicate that slightly more than half of our ascertained cases have no discoverable hereditary basis. If more thorough inquiries were made, the proportion of patients with unfavorable family history might be increased, but the significance of the history in relation to the family stock is open to question in many cases.