While the active part played by the womb in detumescence can no longer be questioned, it need not too hastily be assumed that the belief in the active movements of the spermatozoa must therefore be denied. The vigorous motility of the tadpole-like organisms is obvious to anyone who has ever seen fresh semen under the microscope; and if it is correct, as Clifton Edgar states, that the spermatozoa may retain their full activity in the female organs for at least seventeen days, they have ample time to exert their energies. The fact that impregnation sometimes occurs without rupture of the hymen is not decisive evidence that there has been no penetration, as the hymen may dilate without rupturing; but there seems no reason to doubt that conception has sometimes taken place when ejaculation has occurred without penetration; this is indicated in a fairly objective manner when, as has been occasionally observed, conception has occurred in women whose vaginas were so narrow as scarcely to admit the entrance of a goose-quill; such was the condition in the case of a pregnant woman brought forward by Roubaud. The stories, repeated in various books, of women who have conceived after homosexual relations with partners who had just left their husbands' beds are not therefore inherently impossible.[119] Janke quotes numerous cases in which there has been impregnation in virgins who have merely allowed the penis to be placed in contact with the vulva, the hymen remaining unruptured until delivery.[120] It must be added, however, that even if the semen is effused merely at the mouth of the vagina, without actual penetration, the spermatozoa are still not entirely without any resource save their own motility in the task of reaching the ovum. As we have seen, it is not only the uterus which takes an active part in detumescence; the vagina also is in active movement, and it seems highly probable that, at all events in some women and under some circumstances, such movement favoring aspiration toward the womb may be communicated to the external mouth of the vagina.