It was indeed the failure to understand the vital activity of the semen and the feminine genital canal, co-operating together towards the junction of sperm cell and germ cell, which for so long stood in the way of the proper understanding of conception. Even the genius of Harvey, which had grappled successfully with the problem of the circulation, failed in the attempt to comprehend the problem of generation. Mainly on account of this difficulty, he was unable to see how the male element could possibly enter the uterus, although he devoted much observation and study to the question. Writing of the uterus of the doe after copulation, he says: "I began to doubt, to ask myself whether the semen of the male could by any possibility make its way by attraction or injection to the seat of conception, and repeated examination led me to the conclusion that none of the semen reached this seat." (_De-Generatione Animalium_, Exercise lxvii.) "The woman," he finally concluded, "after contact with the spermatic fluid _in coitu_, seems to receive an influence and become fecundated without the co-operation of any sensible corporeal agent, in the same way as iron touched by the magnet is endowed with its powers." Although the specifically sexual muscular process of detumescence in women--as distinguished from the general muscular phenomena of sexual excitement which may be fairly obvious--is thus seen to be somewhat complex and obscure, in women as well as in men detumescence is a convulsion which discharges a slowly accumulated store of nervous force. In women also, as in men, the motor discharge is directed to a specific end--the intromission of the semen in the one sex, its reception in the other. In both sexes the sexual orgasm and the pleasure and satisfaction associated with it, involve, as their most essential element, the motor activity of the sexual sphere.[121] The active co-operation of the female organs in detumescence is probably indicated by the difficulty which is experienced in achieving conception by the artificial injection of semen. Marion Sims stated in 1866, in _Clinical Notes on Uterine Surgery_, that in 55 injections in six women he had only once been successful; he believed that that was the only case at that time on record. Jacobi had, however, practiced artificial fecundation in animals (in 1700) and John Hunter in man. See Gould and Pyle, _Anomalies and Curiosities of Medicine_, p. 43; also Janke (_Die Willkürliche Hervorbringen des Geschlechts_, pp. 230 et seq.) who discusses the question of artificial fecundation and brings together a mass of data.