Somnambulism (Lat. somnus, sleep, and am-Imlare, to walk), literally, the act of walking in sleep, but usually applied to all the movements of a person who while in a condition of sleep acts his dreams. There are three kinds of somnambulism, viz.: 1, simple, where the somnambulist is apparently in ordinary health, but rises from his bed, walks, runs, or climbs, or sometimes talks or writes, while asleep; 2, morbid, where there is a diseased condition, which admits the manifestation of the duality of the human system, the somnambulist some-times being alternately in the natural and the morbid condition, and frequently while in the latter performing acts of which while awake ho is incapable; and 3, artificial, which is treated under Animal Magnetism. The first class of somnambulists are usually persons of nervous temperament, and the phenomena are generally induced in them either by some violent excitement, or oftener by a morbid condition of the stomach, late suppers, indigestible food, or the like. Some writers advise the placing a wet cloth before their beds, on which they may step, or waking them suddenly in some other way; but such a course is fraught with great danger, as the shock may prove fatal, or at least permanently injurious. - Morbid somnambulism is a condition concerning which we have little positive knowledge, but the phenomena of which are often very striking.

A shy, diffident girl of 14, for instance, of a nervous temperament, but who has exhibited no extraordinary intellectual powers, and has had but very ordinary education, becomes languid, listless, and pale; complains of pain in the side, and perhaps of an unpleasant feeling in the frontal region; after a while, falling asleep in the daytime, she will rise from her chair, and, imagining herself a preacher to a large audience, go through the preliminary exercises of a religious service, and deliver an extempore sermon, the arrangement and language of which far transcend her waking capacity; and this performance may be repeated daily or every other day. In the case we are describing, which in its general features is similar to a considerable number which have occurred in recent times, the subject recovered her health, and the phenomena ceased after two or three years. In some instances they have been followed by the death of the somnambulist. - The development of the double existence is another of the phenomena of morbid somnambulism, not less remarkable than the preceding, and equally well authenticated.

The history of the celebrated seeress of Prevorst, by Dr. Kerner, will be readily recalled; and in many cases the two states are strongly marked, and the subject remains in each for some weeks, being utterly unconscious while in the one of any event which has occurred while in the other. Though resembling it in some particulars, these cases are not to be confounded with those in a state of ecstasy (see Catalepsy), there being none of the physical insensibility or muscular rigidity. The causes and cure of this form of somnambulism are alike obscure. - See Dr. A. J. Kerner, Geschichte zweier Somnambulen (Carls-ruhe, 1824), and "The Seeress of Prevorst," translated into English by Mrs. Catharine Crowe (New York, 1845); Macnish's "Philosophy of Sleep " (1830); Abercrombie "On the Intellectual Powers" (1830); Deleuze's "Critical History of Animal Magnetism" (revised ed., New York, 1846); Colquhoun's "Animal Magnetism" (1851); Reichenbach's Animal Magnetism;" Dr. Sonderis's "Narrative of the Religious Excitement in Sweden;" and Dr. Gibson's "Year of Grace, an Account of the great Irish Revival in 1859" (1860).