insanity, chiefly mania and melancholia, 46 per cent, of females and 40 per cent, of males showed periodicity,--diurnal, monthly, seasonal, or annual, and more marked in women than in men, and in mania than in melancholia,--and adds: "I found that the younger the patient, the greater is the tendency to periodic remission and relapse. The phenomenon finds its acme in the cases of pubescent and adolescent insanity." Conolly Norman, in the article "Mania, Hysterical" (Tuke's _Psychological Dictionary_), states that "the activity of the sexual organs is probably in both sexes fundamentally periodic." Krafft-Ebing records the case of a neurasthenic Russian, aged 24, who experienced sexual desires of urologinic character, with fair regularity, every four weeks (_Psychopathia Sexualis_), and Näcke mentions the case of a man who had nocturnal emissions at intervals of four weeks (_Archiv für Kriminal-Anthropologie_, 1908, p. 363), while Moll (_Libido Sexualis_, Bd. I, pp. 621-623) recorded the case of a man, otherwise normal, who had attacks of homosexual feeling every four weeks, and Rohleder (_Zeitschrift für Sexualwissenschaft_, Nov., 1908) gives the case of an unmarried slightly neuropathic physician who for several days every three to five weeks has attacks of almost satyriacal sexual excitement. Féré, whose attention was called to this point, from time to time noted the existence of sexual periodicity. Thus, in a case of general paralysis, attacks of continuous sexual excitement, with sleeplessness, occurred every twenty-eight days; at other times, the patient, a man of 42, in the stage of dementia, slept well, and showed no signs of sexual excitation (_Société de Biologie_, October 6, 1900). In another case, of a man of sound heredity and good health till middle life, periodic sexual manifestations began from puberty, with localized genital congestion, erotic ideas, and copious urination, lasting for two or three days. These manifestations became menstrual, with a period of intermenstrual excitement appearing regularly, but never became intense. Between the age of 36 and 42, the intermenstrual crises gradually ceased; at about 45, the menstrual crises ceased; the periodic crises continued, however, with the sole manifestation of increased frequency of urination (_Société de Biologie_, July 23, 1904). In a third case, of sexual neurasthenia, Féré found that from puberty, onwards to middle life, there appeared, every twenty-five to twenty-eight days, tenderness and swelling below the nipple, accompanied by slight sexual excitation and erotic dreams, lasting for one or two days (_Revue de Médecine_, March, 1905).