Such paroxysms occur during the early part of the night, one or two hours after bedtime, when sleep is passing from its maximum intensity to an inferior degree of depth. This, moreover, is the time when the controlling power of the sensory apparatus over other portions of the nervous system has already reached its minimum. The spinal centres and those intra-cranial ganglia which do not share in the full measure of this repose are therefore in a condition of relative exaltation. Disturbances of internal origin, consequently, produce inordinate excitement of these waking portions of the nervous apparatus. The abnormal quality of this excitement is attested both by the history of the patient, and by the fact that it does not pervade the whole brain. The distribution of motion through the cerebrum is hindered, so that certain portions of the organ remain asleep while other regions are thrown into a state of tumultuous uproar. Such disconnection of the different organs of the nervous system, by withdrawing particular ganglia from the inhibitory influence of the other centres, gives opportunity for violent explosions of nervous force.
Somewhat similar in their origin are those acts of unconscious violence which sometimes occur during the process of sudden awakening out of sound sleep. The patient is usually a deep but uneasy sleeper, who is only aroused imperfectly and with difficulty when the attempt to awaken him is made. Under such circumstances the disturbance to which he is subjected serves as the exciting cause of a dream which, like the ordinary somnambulist, he puts into action before he is fully waked. On recovering complete consciousness, he may retain no recollection of the events of his dream, and may also experience as great a degree of astonishment at the results of his violence as if he had taken no part in its display. A gentleman of my acquaintance, who had suffered considerable uneasiness regarding burglars, was, one night, startled by a noise in his room. Jumping up suddenly, he grasped a pistol and fired it in the direction of a figure dimly perceived near the bed. On waking fully out of sleep, he found that he had inflicted a wound upon the hand of his wife whose movements had disturbed him. Another unfortunate, who was once under my observation for undoubted insanity, was in like manner aroused out of sleep by a supposed noise, probably heard in a dream. With a pistol in each hand, he commenced firing wildly in every direction, fatally wounding his wife who was in bed at his side. When completely awakened he had no recollection of what had occurred, and was overwhelmed by the event.