Deep and chronic lesions have been observed in the encephalon of onanists, much more frequently than acute diseases. We published, in 1817, a case of chronic arachnitis, which seemed to depend on this cause. The patient was a boy seven years old, who entered the Hospital des Enfans, at the beginning of the preceding year. This child, who was much addicted to masturbation, was usually affected with convulsions during this act. He finally became idiotic. He was extremely repugnant to take exercise, and he remained very quiet. His strength failed, his limbs wasted away, and finally he became affected with almost total blindness. The hearing, and generally the external and internal senses were also much weakened. Galvanism and other remedies were employed in vain. The patient died; and on opening the cadaver, we found a very marked inflammation of the portion of the meninges which follows the course of the superior longitudinal sinus. The surface of the brain, also, appeared to some assistants to be inflamed. In another patient, whose history is stated by Desruelles, in his memoir on the effects of onanism, the substance of the brain was affected. There was paralysis of the left arm, convulsions of the right arm and of the muscles of the face. On opening the cadaver, an encysted abscess was found in the hemisphere of the brain, on the side opposite to the paralysis, and corresponding to the convulsed limbs. Chronic alterations have frequently been found in the cerebellum of onanists. They have been mentioned by some as the cause, by others as the effect of onanism. But even admitting that in some cases these alterations may have been the beginning of this habit, this fact shows the bond which unites the genital organs and the cerebellum, and renders more probable the influence which they may exercise upon it. In fact, when the disease of one organ deranges the functions of another, we may be satisfied that an opposite result is possible. Farther, it would be impossible, in most of the cases of which we speak, to distinguish whether the cerebral affection or the masturbation had precedence. The only thing positively known is their coincidence; and this latter has appeared too frequently not to attract attention. We will mention several instances of it. A female, addicted at an early age to the pleasures of venery, finally indulged in prostitution; she was at the same time addicted to onanism, and at last became affected with nymphomania. Ashamed of her situation, she submitted to cauterization of the clitoris, but without any good result. She finally died; and we found chronic irritation, with induration of the middle lobe of the cerebellum. Small sinuses, with callous edges, indicated that an inflammation had existed for a long time in this organ.