Diogenes Laertius states that Theon the philosopher, was a sleep-walker. Galen slept whilst on a road, and pursued his journey until he was awakened by tripping on a stone. Felix Plater fell asleep while playing on the lute, and was only startled from his slumbers by the fall of the instrument. There is no doubt but that in somnambulists the intellectual functions are not only active, but frequently more developed than when the individual is awake. Persons in this state have been known to write and correct verses, and solve difficult problems, which they could not have done at other times. In their actions and locomotion they are more cautious, and frequently more dexterous, than when awake. They have been known to saddle and bridle horses, after having dressed themselves; put on boots and spurs, and afterwards ride considerable distances from home and back again. A sleep-walker wandering abroad in winter complained of being frozen, and asked for a glass of brandy, but expressed violent anger on being offered a glass of water. The celebrated sect of _Tremblers_, in the Cevennes mountains, used to rove about in their sleep, and, although badly acquainted with the French language, expressed themselves clearly and put up prayers in that tongue, instead of the Latin _Pater_ and _Credo_ which they had been taught. A singular phenomenon in some cases of this affection is that of walking about without groping, whether the eyelids are closed or open. Somnambulism has been known to be hereditary: Horstius mentions three brothers who were affected with it at the same period; Willis knew a whole family subject to it. It is not generally known that the subject of the French dramatic piece called "La Somnambule" was founded on fact. Singular faculties have been developed in the mental condition. Thus a case is related of a woman in the Edinburgh infirmary, who during her paroxysm not only mimicked the manner of the attendant physicians, but repeated correctly some of their prescriptions in Latin.