The exact relation between these different degrees of somnambulism has been further elucidated by MM. Ball and Chambard.[75] Starting with the proposition that normal healthy existence is a state in which the functions of organic life furnish a basis for nervous sensibility and motion, by means of which the imaginative faculties (imagination and memory), associated with the coördinative faculties (attention, judgment, volition), are sufficiently stimulated to maintain a state of consciousness, they show that the first stage of sleep consists in the suppression of bodily motion and sensibility. The second stage consists in the further suppression of the coördinative faculties. The third stage is marked by the loss of memory and imagination. In the most profound and perfect sleep the functions of organic life alone remain. The process of awaking consists in the revival of the faculties in the inverse order of their extinction. Dreams occur during the period in which motion, sensation, and the coördinative faculties are in abeyance; but somnambulism may accompany each of the stages of sleep. Its simplest form is perhaps the rarest; corresponding to Maury’s fifth variety. In this form the functions of organic life are intact; motion and sensibility seem unchanged; the intellectual faculties display their usual activity; but the ordinary consciousness is never aroused. So far as the normal life of the subject is concerned, he is active, sensible, intelligent, but unconscious; and when the paroxysm is terminated memory contains no account of its events. Such paroxysms may occur but once in the life-time of an individual, or they may be repeated at stated intervals, constituting an alternate succession of mental states without connection in consciousness. This is called the somnambulic life, or double consciousness, several examples of which will be related upon another page. The second form of somnambulism results from the abolition of consciousness and the more or less complete suppression of the coördinative faculties of the mind. Memory and imagination, released in great measure from the control of the higher intellectual faculties, and excited by such vestiges of sensation as still persist, create a species of delirium in which mutilated sensations, half formed thoughts and disproportioned volitions combine to produce a variety of actions. In this condition the patient dreams, and acts out his dream. He is a somnambulic dreamer. In the third degree of somnambulism, consciousness and the entire range of intellectual faculties have disappeared. The individual resembles a creature from which the cerebral hemispheres have been removed. He is little better than a living automaton, guided only by impressions received from without. In this condition the movements of the body may become wholly responsive to the will of another--a prominent characteristic of artificial somnambulism or hypnotism.