is said that there is often no physical sign of the menses for six months at a time. These observations are noteworthy, though they clearly indicate, on the whole, that primitiveness in race is a very powerless factor without a cold climate. On the other hand, again, there is some reason to suppose that in Europe there is a latent tendency in some women for the menstrual cycle to split up further into two cycles, by the appearance of a latent minor climax in the middle of the monthly interval. I allude to the phenomenon usually called _Mittelschmerz_, middle period, or intermenstrual pain. Since the investigations of Goodman, Stephenson, Van Ott, Reinl, Jacobi, and others, it has been generally recognized that menstruation is a continuous process, the flow being merely the climax of a menstrual cycle, a physiological wave which is in constant flux or reflux. This cycle manifests itself in all a woman's activities, in metabolism, respiration, temperature, etc., as well as on the nervous and psychic side. The healthier the woman is, the less conscious is the cyclic return of her life, but the cycle may be traced (as Hegar has found) even before puberty takes place, while Salerni has found that even in amenorrhoea the menstrual cycle still manifests itself in the temperature and respiration. (_Rivista Sperimentale di Freniatria_, XXX, fasc. 2-3.) For a summary of the phenomena of the menstrual cycle, see Havelock Ellis, _Man and Woman_, fourth ed., revised and enlarged, Ch. XI; "The Functional Periodicity of Women." Cf. Keller, _Archives Générales de Médecine_, May, 1897; Hegar, _Allgemeine Zeitschrift für Psychiatrie_, 1901, Heft 2 and 3; Helen MacMurchy, _Lancet_, Oct. 5. 1901; A.E. Giles, _Transactions Obstetrical Society London_, vol. xxxix, p. 115, etc.