Many frequently occurring illnesses are mentally determined, though they consist of real disturbances of the normal functioning of one or more physical organs. They are called organ neuroses. The most familiar form of organ neurosis is neurasthenia, as it is called, known in German as nervous weakness. It was first described by an American nerve specialist in the first half of the nineteenth century, and was attributed to the allegedly shattering effects on the nervous system of railway travel, which was then new and unfamiliar. The causes of the neurasthenic condition are sexual malpractices. From the earliest ages the most terrifying beliefs have been current concerning the consequences of self-gratification, that is the attainment of sexual pleasure by practices on one’s body. To distinguish between them a careful physical examination is necessary as well as a psycho-analytic examination. Should these reveal nothing suspicious, attention should be turned to the patient’s sex life.