SOMNAMBULISM, a word of modern origin, which means strictly and etymologically sleepwalking; it is however generally used in a more extended signification to comprehend all the phenomena that take place when a person, apparently insensible to external objects, acts as if he were in a state of consciousness : and this is the sense which the word will bear in this article. hi. Bertrand, iu his ` Traite du Spmnambulisme' (8vo., Paris, 1823), divides those phenomena into four classes : 1, essential (or proper) somnambulism, which arises from some particular disposition of the nervous system in persons who in other respects apparently enjoy perfect health ; 2, symptomatic (or morbid) somnambulism, which occurs in the course of certain diseases; 3, artificial somnambulism, rhich is occasioned by the proceedings employed in animal magnetism or mesmerism ; and, 4, ecstatic som nambulism, which is the result of a sort of religious enthusiasm. The same division of the subject will be here adopted.
I. E,sential (or Proper) Somnambulism is intimately connected with the subject of sleep and dreaming; and iu fact "a semnambulator," as Dr. Pritchard says, "is nothing but a dreamer who is able to act his dreams." [ DREAMS.] [ SLEEP, in NAT. HIST. DIV. ] As a minute inquiry into the physiology of these two pheno mena would here be out of place, the reader must consult the articles already given on these subjects. This form of somnambulism was noticed by the ancients. The author of the treatise 'Do Morbo Sacro,' that commonly goes under the name of Hippocrates, says that "he knew many persons who used to groan and cry out in their sleep, and others that seemed to pant for breath (myouivous), and others that would get up and run out of the house and act like madmen till they were awakened, after which they were in good health and sound sense as before, only rather pale and weak" (torn. i., p. 588, ed.
Kiihn). Aristotle tells us that "there are individuals who rise in their sleep and walk about, seeing as clearly as those that arc awake." Dio genes Laertius mentions (` De Vitis Philosophorum, Pyrrho,' lib. ix.) that a Stoic philosopher named Theon was a sleepwalker; and Galen says (' De Metu Musculorum: lib. 1, cap. 4, tom. iv. p. 435, 436, ed. Kuhn) that he would not believe that people ever fell asleep while walking, until one night when walking along the road he did so him self, and went on for about a furlong, sleeping and dreaming, till at last be was awakened by kicking against a stone. "And this," adds
he, " is the reason why people cannot go on walking for any distance iu their sleep, because they cannot meet with a perfectly smooth road;" in which he is net quite correct, as we often find that both the bodily and intellectual powers of the individual are more active and developed in his sleep then when he is awake, and that he is then able to perform feats which at any other time he would shudder at. The instances on record of this species of somnambulism are so numerous that it is difficult to select the most interesting; one or two examples however must be given, and for a more copious collection the reader must be referred to some of the works whose titles will be given in the following part of this article.
Several interesting eases of somnambulism will be found in Mura tend work,' Forts della Fantasia Iltmiana some of them given ou the authority of Oassendi. One of Gasseudi's somnambulists used to rise and dress himself in his sleep, go down to the cellar and draw wine from a cask. lie appeared to see in the dark as well as In a clear day ; but when ha awoke, either in the street or cellar, he was obliged to grope ani feel his way back to his bed. He always answered his wife as if awake, but in the morning recollected nothing of what had Another sleep-walker, a countryman of Oasaendi's, primed on stilts over a swollen torrent in the night, but on awaking was afraid to return before daylight, or until the water had subsided. This species of somnambulism has been known to be hereditary. thirsting, in his work Do Nature, Differentiis, et Causis eorum qui Donnientes ambulant' (sew' de Noctanibulonibus '), Lips., 1595, 8vo., p. 172, mentions three brothers who were with it at the same time ; and Willis knew a whole family that was subject to it. Perhaps however these may rather be considered as instances of the influence of example and of the power of unconscious imitation, which some times renders it in a manner contagious. Of this there is a curious example given by Dr. l'ezzi, in a work entitled Scretti di Medico Argos nento; Venez., 1813. It appears that his nephew, after reading more than once the history of a somnambulist, was himself seized with this affection ; and also that the servant who attended him soon began to exhibit in his own person similar phenomena.