According to _Hensen_, the direct stimulation of the sexual impulse proceeds by way of the dorsal nerve of the (penis or) clitoris; he assumes, however, that certain states of the reproductive glands are able to induce an increase in the irritability of the centres connected with the aforesaid nerves. In women it certainly appears that particular states of the ovary have a stimulating or inhibiting influence respectively on sexual excitement, so that we might ascribe to the ovaries the rôle of a regulator of the sexual impulse. The processes that occur in the ovary at the time of the ripening and rupture of the graafian follicle, and the resulting tension of the follicular wall, induce by stimulation of the ovarian nerves an increased sensibility of the central zones, and produce in a menstruating female a condition of increased sexual excitability, so that slight stimuli will give rise to a powerful orgasm more readily than would otherwise be the case, when the reflex irritability of the centre is less pronounced and the sexual impulse is consequently less intense. Still more than during these ordinary menstrual processes may this stimulation be effective at the time of the menarche, when the changes in the ovary occur for the first time and with the greatest intensity, so that at this time the individual may be especially susceptible to sexual stimulation. At such times of sexual excitement, very slight external peripheral stimuli, in the form either of tactile stimulation of the sensory nerves of the skin and the external genital organs, or of stimulation of the imaginative and perceptive faculties of the brain, suffice to induce a powerful increase of the sexual impulse; whereas at other times, at which no particular sexual excitement exists, much stronger stimuli are needed to produce such an effect. Thus the sexual impulse in women is more readily and more powerfully increased in proportion as the central organ is in a condition of temporarily enhanced excitability in consequence of the condition of the ovaries. The gratification of this impulse, the act of copulation, produces the specific sensation of sexual pleasure; in the female this is effected chiefly by friction of the glans clitoridis, the organ when erect projecting downwards at a right angle, and pressing upon the intromitted penis—the friction of the glans produces powerful mechanical stimulation of the numerous plexuses of sensory nerve fibres, which terminate in the genital corpuscles of _Krause_. In woman, then, we find in the ovary the place of origin and the means of regulation of the sexual impulse, and in the clitoris we find the seat of the specific sensation of sexual pleasure.