A rich literature exists of cases in which mental abnormalities occurred in psychopathically predisposed individuals as a result of menstruation. Thus, _von Krafft-Ebing_ reports a case in which, during menstruation, a mentally undeveloped woman murdered her husband; and another case in which to chronic weak-mindedness and chronic delusional insanity were superadded during menstruation peculiar attacks having the character of psychical storms. _Tuke_ reports a case in which a mother, in a state of alcoholic excess during menstruation, murdered her daughter. _Pelmann_ records acts of pyromania committed during menstruation by a girl seventeen years of age. _Mabille_ records a case in which a woman suffering from severe mental disorder was affected during menstruation by impulsive kleptomania, whilst after the periods the memory of what had happened passed away. _Philo-Indicus_ records the case of a woman suffering from severe neuropathy who at the menstrual periods exhibited great irritability, experienced marked sexual excitement, and had suicidal impulses, and who on one occasion attempted to murder a female friend who had refused to assist her in the practice of sexual aberrations. _Giraud_ describes a woman suffering from passive melancholia, in whom during menstruation horrible fantastic ideas occurred. _Ball_ records the case of a woman who suffered always from acute mental disorder during menstruation, and who, in one of these attacks, murdered her son. _Kowalewski_ reports a case of chronic imbecility, in which during menstruation attacks of precordial anxiety developed, and in the course of one of these attacks the patient set fire to her own house. “In such cases,” remarks _Kowalewski_, “menstruation represents the last drop that makes the full goblet overflow.” In addition, we meet with cases in which the influence of menstruation is so powerful that it must be regarded as the principal cause of the psychosis. We must then speak of a true menstrual psychosis, the impulse to which is supplied by the normal or abnormal changes occurring in the process of menstruation, and characterized by the menstrual periodicity and the brief duration of the attacks. These are the characteristics of the menstrual psychoses of the menarche and of the climacteric period; and such cases occur also during the period of full menstrual activity.