Such a case was observed by _Wille_. Under the influence of menstruation and of a trifling source of mental disturbance (having soldiers billeted on them in a quiet country village), a young woman aged twenty-one, whose mental health had previously been good, had a sudden attack of anxiety, succeeded by a violent but transitory mania, lasting five or six hours; after a short free interval came another attack, this time lasting several days. Similar cases were recorded by _Friedmann_. A blooming and healthy maid-servant eighteen years of age (some mental unsoundness was recorded in both grandfather and aunt on the maternal side) fell asleep in a chair a few days before menstruation, awakened with a start, was subsequently disordered in mind, though tranquil, with many hallucinations, listening to voices which repeated monotonously “they come,” was drowsy, and slow to answer when spoken to. On the third day she was recovered, her mind being clear and normal; she was not fully aware of what had happened. Since this attack, her mind has been free from disorder, during menstruation as well as at other times. She is said to have had a similar attack about four years ago, that is, at the commencement of puberty.—A girl aged thirteen, quite healthy, not nervous, physically rather powerful, with quite healthy family history. Complaints of having suffered for two days from general sense of depression with pains in the abdomen; during the afternoon was lying on a sofa, but suddenly sprang up, looked extremely anxious and confused, ran about the room, begged to be protected from the black man, etc., her speech was disconnected, gabbling, and difficult to understand. After two hours she became quiet, and fell into a sound sleep, from which she awoke calm and quite forgetful of what had passed. On the following day menstruation appeared for the first time, with abdominal pains, but without any mental abnormality. During the subsequent six years she has remained quite well.