THE PHILOSOPHY OF SLEEP. CHAPTER I. INTRODUCTION. SLEEP is the intermediate state between wakefulness and death: wakefulness being regarded as the active state of all the animal and intellectual functions, and death as that of their total suspension. Sleep exists in two states; in the complete and incomplete. The former is characterized by a torpor of the various organs which compose the brain, and by that of the external senses and voluntary motion. Incomplete sleep, or dreaming, is the active state of one or more of the cerebral organs while the remainder are in repose: the senses and the volition being either suspended or in action according to the circumstances of the case. Complete sleep is a temporary metaphysical death, though not an organic one-the heart and lungs performing their offices with their accustomed regularity under the control of the involuntary muscles. Sleep is variously modified, as we shall fully explain hereafter, by health and disease. The sleep of health is full of tranquillity. In such a state we remain for hours at a time in unbroken repose, nature banqueting on its sweets, renewing its lost energies, and laying in a fresh store for the succeeding day. This accomplished, slumber vanishes like a vapor before the rising sun; languor has been succeeded by strength; and all the faculties, mental and corporeal, are recruited. In this delightful state, man assimilates most with that in which Adam sprang from his Creator's hands, fresh, buoyant, and vigorous; rejoicing as a racer to run his course, with all his appetencies of enjoyment on edge, and all his feelings and faculties prepared for exertion. Reverse the picture, and we have the sleep of disease. It is short, feverish, and unrefreshing, disturbed by frightful or melancholy dreams. The pulse is agitated, and, from nervous excitation, there are frequent startings and twitchings of the muscles. Nightmare presses like an incarnation of misery upon the frame-imagination, distempered by its connexion with physical disorder, ranging along the gloomy confines of terror, holding communication with hell and the grave, and throwing a discoloring shade over human life. Night is the time for sleep; and assuredly the hush of darkness as naturally courts to repose as meridian splendor flashes on us the necessity of our being up at our labor. In fact, there exists a strange, but certain sympathy between the periods of day and night, and the performance of particular functions during these periods. That this is not the mere effect of custom, might be readily demonstrated. All nature awakes with the rising sun. The birds begin to sing; the bees to fly about with murmurous delight. The flowers which shut under the embrace of darkness, unfold themselves to the light. The cattle arise to crop the dewy herbage; and "man goeth forth to his labor until the evening." At close of day, the reverse of all this activity and motion is observed. The songs of the woodland choir, one after another, become hushed, till at length twilight is left to silence, with her own star and her falling dews. Action is succeeded by listlessness, energy by languor, the desire of exertion by the inclination for repose. Sleep, which shuns the light, embraces darkness, and they lie down together under the sceptre of midnight. From the position of man in society, toil or employment of some kind or other is an almost necessary concomitant of his nature-being essential to healthy sleep, and consequently to the renovation of our bodily organs and mental faculties. But as no general rule can be laid down as to the quality and quantity of labor best adapted to particular temperaments, so neither can it be positively said how many hours of sleep are necessary for the animal frame. When the body is in a state of increase, as in the advance from infancy to boyhood, so much sleep is required, that the greater |