The phenomena of ordinary somnambulism are manifested, like the dreams out of which they arise, during the period of sleep. But, while dreams most frequently occur during the later portion of the night, after the deepest sleep is past, somnambulism usually occurs in the earlier part of the night, during the deepest sleep. As a consequence of this fact, consciousness is seldom affected by the molecular play of the brain during the somnambulic excursion. The sleepwalker knows nothing, and remembers nothing of the incidents in which he has been an active agent; while the dreamer seems to be more nearly awake. His consciousness is partially aroused by the play of memory and of imagination, and he can remember the spectacle which constituted his dream. The phenomena of somnambulism necessitate the participation of a larger number of faculties than are needed for the production of a dream, but their activities are coördinated upon a plane, so to speak, lower than the platform upon which the elements of dreams are arranged. Consequently, though the elements of the somnambulic process may be far more numerous and various than the elements of a dream, they may be less capable of rising into the realm of consciousness. Such a process may differ from the phenomena of ordinary life only in the fact of unconsciousness; and, when concluded, it leaves no traces in the memory of the waking state. In other instances, on the contrary, so many nervous functions may be suppressed, and so great may be the intensity of the remaining cerebral processes, that the resulting phenomena scarcely differ from an ordinary dream in which consciousness is aroused, and the waking memory is durably impressed. Between these extremes lie opportunities for an indefinite number of combinations; consequently the forms and degrees of somnambulism present a very great variety of manifestation. Maury[74] reduces these to five principal forms: First, simple movement of the limbs in connection with that partial sleep of the intellectual faculties which produces ordinary dreams. Second, _somniation_, a state in which the patient unconsciously performs such actions as have become so far habitual that, though complicated in their character, they constitute genuine cerebral reflexes. Third, _noctambulism_, or sleep-walking, in which the action, though complicated in its character, and different from the ordinary waking occupations of the patient, appears to be the result of automatic processes, constituting a dream that is acted out in time and space. Fourth, _somnambulism_ with exaltation of the faculties, producing delirium with conscious movements during the crisis. Fifth, _somnambulic life_, or double consciousness, in which, with the exception of certain special modifications of intelligence, the conduct of the patient during the paroxysm does not perceptibly differ from that of the waking state, so that the subject seems to experience two successive though disconnected personalities.