Tait, Provincial Medical Journal, May, 1891; J. Beard, The Span of Gestation, 1897, p. 69. Lawson Tait is reduced to the assertion that ovulation and menstruation are identical.
As Moll points out, even the secondary sexual characters have undergone a somewhat similar change. The beard was once an important sexual attraction, but men can now afford to dispense with it without fear of loss in attractiveness. (Libido Sexualis, Band I, p. 387.) These points are discussed at greater length in the fourth volume of these Studies, "Sexual Selection in Man."
It is not absolutely established that in menstruating animals the period of menstruation is always a period of sexual congress; probably not, the influence of menstruation being diminished by the more fundamental influence of breeding seasons, which affect the male also; monkeys have a breeding season, though they menstruate regularly all the year round.