In the former connection, _Brierre de Boismont_ undertook an investigation which showed that in women suffering from mental disorder, an exacerbation of that disorder was to be observed during menstruation. _Schlager_, who regards the menstrual process as possessing when anomalous a high significance for the development and course of mental disturbances, observed that in 33 per cent. of women suffering from mental disorder, the menstrual state had an unfavorable influence upon the course of that disorder, inasmuch as it led to an increased irritability; in the rest of the cases, however, menstruation was without influence upon the course of the ordinary chronic psychoses. In the cases that were unfavorably influenced, epileptic attacks usually became more frequent, and chronic melancholia became much more profound. _Schröder_ observed in chronic forms of melancholia that during menstruation the sadness became intolerable and was associated with a suicidal tendency; in chronic maniacal forms of mental disorder, the excitement underwent an increase during menstruation. _Von Krafft-Ebing_, as a result of his investigations into insanity during menstruation, came to similar conclusions with regard to the unfavorable influence of the menstrual process. _Algeri_ likewise states that menstruation notably aggravates the cerebral symptoms in the course of mental disorders. Other authors, _Marcé_ and _Kowalewski_ for instance, whilst emphasizing the powerful influence exerted by menstruation on any existing psychosis, point out that in some instances, as in states of mental and physical depression, this influence is for the worse; but in other instances, especially in states of maniacal excitement, the condition of the patient undergoes notable amelioration during menstruation. _Schäfer_ also, in his researches into the relations between the processes of menstruation and psychoses, discovered that anomalies in the course of menstruation ran almost parallel with anomalies in the course of mental activity. In psychopathically predisposed women, disorders of menstruation, such as amenorrhœa, delayed menstruation, and dysmenorrhœa, are more effective than the normal process of menstruation in evoking manifestations of psychical abnormalities previously latent, and in leading to attacks of precordial anxiety, pathological emotional states, melancholic seizures, epilepsy in all its varieties, and impulsive manifestations, such as pyromania, kleptomania, infanticide, homicide, etc. As results of a special predisposition may appear in this connection, congenital imbecility, idiocy, melancholia, and chronic weak-mindedness.