During coitus, the uterine muscle is also active. During strong sexual excitement, the uterus descends in the pelvis, the downward movement being increased by the pressure on the woman’s abdomen. The os uteri externum is drawn open, and the aperture, hitherto flattened, now becomes rounded. At the same time, the secretion of the cervical glands is expelled, and small quantities of semen are sucked into the cervical canal. The _plicae palmatae_ offer a certain hindrance to the entrance of the semen; but the surface of the interior of the canal is rendered much smoother by the free secretion of mucus by the cervical glands. Further, it appears highly probable that during the excitement of coitus, the mouths of the Fallopian tubes, ordinarily more or less tightly closed, become widely opened, so that the entrance of the spermatozoa is favored. The muscular movements of the uterus were observed by _J. Beck_ in a woman suffering from prolapse. During sexual excitement, the os uteri opened and closed rapidly five or six times in succession, remaining at last firmly closed. Further, in bitches on heat, _Basch_ and _Hoffmann_ observed the vaginal portion of the cervix to descend in the vagina, the os uteri opened, mucus was extruded, and the os was then retracted. _Hohl_, _Litzmann_, and others have reported, that in women endowed with great nervous susceptibility, friction of the vaginal portion of the cervix with the finger arouses sexual sensation, with rounding of the os uteri externum, descent of the uterus, and hardening of the vaginal portion; this latter is regarded by _Graily Hewitt_ and by _Wernich_ as a necessary accompaniment of copulation. _Henle_ believes that the hardening and protrusion of the vaginal portion of the cervix are due to a change in the tension of the delicate vessels of this structure, which have an exceptionally thick muscular coat; _Rouget_ compares the mechanism with that by which erection of the penis is produced. These authors consider that sexual excitement is indispensable for the erection of the vaginal portion of the cervix.