Riolan (_Anthropographia_, 1626, p. 294) referred to the
constriction and dilation of the vulva under the influence of
sexual excitement. It is said that in Abyssinia women can, when
adopting the straddling posture of coitus, by the movements of
their own vaginal muscles alone, grasp the male organ and cause
ejaculation, although the man remains passive. According to
Lorion the Annamites, adopting the normal posture of coitus,
introduce the penis when flaccid or only half erect, the
contraction of the vaginal walls completing the process; the
penis is very small in this people. It is recognized by
gynaecologists that the condition of vaginismus, in which there is
spasmodic contraction of the vagina, making intercourse painful
or impossible, is but a morbid exaggeration of the normal
contraction which occurs in sexual excitement. Even in the
absence of sexual excitement there is a vague affection,
occurring in both married and unmarried women, and not, it would
seem, necessarily hysterical, characterized by quivering or
twitching of the vulva; I am told that this is popularly termed
"flackering of the shape" in Yorkshire and "taittering of the
lips" in Ireland. It may be added that quivering of the gluteal
muscles also takes place during detumescence, and that in Indian
medicine this is likewise regarded as a sign of sexual desire in
women, apart from coitus.

A non-medical correspondent in Australia, W.J. Chidley, from whom
I have received many communications on this subject, is strongly
of opinion from his own observations that not only does the
uterus take an active part in coitus, but that under natural
conditions the vagina also plays an active part in the process.
He was led to suspect such an action many years ago, as well by
an experience of his own, as also by hearing from a young woman
who met her lover after a long absence that by the excitement
thus aroused a tape attached to the underclothes had been drawn
into the vagina. Since then the confidences of various friends,
together with observations of animals, have confirmed him in the
view that the general belief that coitus must be effected by
forcible entry of the male organ into a passive vagina is
incorrect. He considers that under normal circumstances coitus
should take place but rarely, and then only