The sexual impulse, as sensation, perception, and impulse, is, according to _von Krafft-Ebing_, a function of the cerebral cortex; a centre for the sexual sense has not as yet, however, been localized. The close relations which obtain between the sexual life and the sense of smell lead to the supposition that the sexual and the olfactory spheres of the cerebral cortex are in close proximity one with the other. The development of the sexual life has its beginnings in the organic sensations of the developing reproductive glands. A mutual dependence now arises between the cerebral cortex as place of origin of sensations and perceptions, and the organs of generation. By anatomico-physiological processes these now give rise to sexual perceptions, representations, and impulses. The cerebral cortex, by apperceived or reproduced sensuous perceptions, influences the organs of generation. This influence is effected by the intermediation of the centres of vascular innervation and ejaculation, which are situated in the lumbar enlargement of the spinal cord, and are certainly in close proximity one with the other. Both are reflex centres. The psycho-physiological process embraced in the conception of the sexual impulse is according to _von Krafft-Ebing_ constituted in the following manner: I. Of the central or peripherally aroused perceptions. II. Of the pleasurable sensations associated with these. Hence arises the impulse to sexual satisfaction (libido sexualis). This impulse becomes stronger in proportion as cerebral excitement, consequent on appropriate perceptions and the working of the imagination, strengthens the intensity of these pleasurable sensations. If the conditions are favorable to the performance of the sexual act by means of which satisfaction is attained, the continually increasing impulse finds expression in action; in other circumstances, inhibitory perceptions intervene, sexual excitement diminishes, the activity of the centre for erection is inhibited, and the sexual act itself is prevented. In the case of civilized humanity the ready action of such perceptions for the inhibition of the sexual impulse is necessary and decisive. On the strength of the impulsive perceptions the constitution and various organic processes have an important influence; on the strength of the inhibitory perceptions, education and the cultivation of self-control are powerfully operative.