Heredity varies with the psychoses, having its greatest influence in the transmission of manic-depressive attacks, epileptic and hysterical conditions, nervousness, compulsive and impulsive insanity, sexual perversions and morbid personalities (Kraepelin). As the result of a study of two thousand cases, Pilcz[69] (1907) found that in alcoholism heredity was most likely to manifest itself in the form of alcoholism, epilepsy and imbecility or manic-depressive psychoses. In the progenitors of epileptics he found epilepsy and migraine. Apoplectics showed a family history of paralysis, arteriosclerosis, senile dementia or melancholia. Senile dementia preceded paralysis, arteriosclerosis, feeblemindedness and dementia praecox. Tabes and paralysis apparently frequently precede paralysis and dementia praecox. The various forms of alcoholic psychoses furthermore show a tendency to repeat themselves in the offspring of alcoholics. Similar heredity is said to be the general rule in manic-depressive psychoses, epilepsy and alcoholism, and to a less extent in arteriosclerosis. Heredity, in so far as it is related to mental diseases, may be said to be largely a question of the transmission of a neuropathic or psychopathic constitution or predisposition. Various psychoses are now held to be the direct result of constitutional causes or hereditary influences. This is probably true of manic-depressive insanity, Huntington's chorea, involution melancholia, dementia praecox, paranoia and paranoid conditions, epileptic psychoses, the psychoneuroses and neuroses, psychopathic personality and mental deficiency. It is true that some of these conditions develop as the immediate results of certain predisposing factors and that in frequent instances no evidences of heredity can be found. It is also true that various authorities maintain that a predisposition to the development of certain psychoses may be acquired. If, however, we assume that the above mentioned psychoses are constitutional in their nature and due primarily to heredity, it may be definitely stated that, based on recent statistical studies, hereditary influences account for from fifty-five to sixty per cent of the mental cases admitted to our institutions. It may be pointed out, as an objection to this suggestion, that although manic-depressive psychoses often develop in an emotionally unstable or cyclothymic personality and dementia praecox is associated with certain peculiarities of makeup, not all of these cases show clear evidences of constitutional origins. This is unquestionably true. It is equally true, on the other hand, that heredity is also probably very often a factor in the production of the senile and arteriosclerotic conditions, various nervous diseases, alcoholism and drug habits.