The phenomena of detumescence culminate, however, and have their most obvious manifestation in motor activity. The genital act, as Vaschide and Vurpas remark, consists essentially in "a more and more marked tension of the motor state which, reaching its maximum, presents a short tonic phase, followed by a clonic phase, and terminates in a period of adynamia and repose." This motor activity is of the essence of the impulse of detumescence, because without it the sperm cells could not be brought into the neighborhood of the germ cell and be propelled into the organic nest which is assigned for their conjunction and incubation. The motor activity is general as well as specifically sexual. There is a general tendency to more or less involuntary movement, without any increase of voluntary muscular power, which is, indeed, decreased, and Vaschide and Vurpas state that dynamometric results are somewhat lower than normal during sexual excitement, and the variations greater.[114] The tendency to diffused activity of involuntary muscle is well illustrated by the contraction of the bladder associated with detumescence. While this occurs in both sexes, in men erection produces a mechanical impediment to any evacuation of the bladder. In women there is not only a desire to urinate but, occasionally, actual urination. Many quite healthy and normal women have, as a rare accident supervening on the coincidence of an unusually full bladder with an unusual degree of sexual excitement, experienced a powerful and quite involuntary evacuation of the bladder at the moment of orgasm. In women with less normal nervous systems this has, more rarely, been almost habitual. Brantôme has perhaps recorded the earliest case of this kind in referring to a lady he knew who "quand on lui faisait cela elle se compissait à bon escient."[115] The tendency to trembling, constriction of throat, sneezing, emission of internal gas, and the other similar phenomena occasionally associated with detumescence, are likewise due to diffusion of the motor disturbance. Even in infancy the motor signs of sexual excitement are the most obvious indications of orgasm; thus West, describing masturbation in a child of six or nine months who practiced thigh-rubbing, states that when sitting in her high chair she would grasp the handles, stiffen herself, and stare, rubbing her thighs quickly together several times, and then come to herself with a sigh, tired, relaxed, and sweating, these seizures, which lasted one or two minutes, being mistaken by the relations for epileptic fits.[116]