In artificial somnambulism--the hypnotism of Braid--the spinal cord acquires a very high degree of susceptibility to sensorial impressions, and the brain is even more incapable than in natural somnambulism of asserting its superiority. But the consideration of this interesting branch of the subject does not enter into the plan of the present work. The _causes_ of somnambulism are generally to be found inherent in the organism of the individual, though they may be excited to activity by many circumstances which are capable of exhausting the nervous system or producing emotional disturbance. Young persons are more subject than those of maturer age, and there are few children who do not exhibit at some time or other manifestations of the condition in question, such as muttering and talking in their sleep, laughing, crying, or getting out of bed. Persons of the nervous temperament are those most liable to be affected. In four cases of chorea which have come under my care, the subjects were sleep-walkers in their youth, and the young lady whose case I have related was choreic at the time. In regard to the _treatment_ there is not much to be said. In the great majority of cases the affection yields readily to appropriate measures; the most efficacious of which consists in means adapted to break up the habit. This may be done by waking the patient before the expected paroxysm, or by placing a tub of cold water so that the feet will be put into it on the attempt to leave the bed. Full exercise in the open air, the avoidance of luxurious habits, and sleeping with the head well raised, are always beneficial. Of medicines, I have no experience except with the bromide of potassium, and those calculated to improve the tone of the nervous system. The former I have used in two cases with entire success. One of them was that of the young lady, the details of whose case I have related; the other that of a gentleman, forty years of age, who became somnambulic from mental excitement, due to the extensive business operations in which he was engaged. Large doses of this remedy--forty to sixty grains taken at bedtime, and smaller doses, ten to thirty grains, taken twice through the day--broke up the habit entirely in a few weeks. Among the other remedies, I have employed phosphorus, strychnia, and iron with manifest advantage. Cold baths are generally useful. I am acquainted with a young lady who cured herself by taking a cold bath every night just before going to bed. The so-called antispasmodics can scarcely be useful. Much may be done also by suitable mental training. The reading of exciting fictions, and the witnessing of sensational theatrical exhibitions, are always prejudicial to persons subject to attacks of somnambulism. CHAPTER VIII. THE PATHOLOGY OF WAKEFULNESS.