+============================================================+ | Organic Life. | | | Conscious Life. | | | | Imaginative Faculties. | | | | | Coördinative Faculties. | | | | | | Special Sensation and Voluntary Motion.| |----+----+----+----+----+-----------------------------------| |XXXXXXXXXXXXXXXXXXXXXX | Normal life. | |------------------------------------------------------------| |XXXXXXXXXXXXXXXXX |First stage of sleep--Hypnagogic | | | hallucinations. | |------------------------------------------------------------| |XXXXXXXXXXXX |Second stage of sleep--Dreaming. | |------------------------------------------------------------| |XXXXXXX |Third stage of sleep. | |------------------------------------------------------------| |XX |Profound sleep. | |------------------------------------------------------------| |XXXXXXX |First stage of waking. | |------------------------------------------------------------| |XXXXXXXXXXXX |Second stage of waking--Dreams. | |------------------------------------------------------------| |XXXXXXXXXXXXXXXXX |Third stage of waking--Hypnagogic | | | hallucinations. | |------------------------------------------------------------| |XXXXXXXXXXXXXXXXXXXXXX |Complete awakening. | +------------------------------------------------------------+
It was formerly believed that during the time of sleep all the processes of assimilation and nutrition throughout the body are increased,--in short, that it is the season of repair for the waste of tissue incurred during the hours of wakeful activity. While it is true that in sleep the expenditure of force is greatly reduced, the more exact researches of modern physiologists indicate a universal reduction in the rate of all the vital processes. The final result, however, is a general renewal of energy, because the aggregate income of the tissues is greater than their outgo during the suspension of conscious activity. The following observations make very apparent the fact of a reduction of physiological activity:
_Respiration._--The process of breathing is conducted with greater deliberation during the period of sleep. This reduction is one of the most notable of the circumstances that first attract the attention of the spectator who observes a sleeping person. The average number of respirations per minute, in an adult of twenty-five to thirty years of age, is sixteen. Quetelet remarked[3] that during sleep this number was diminished by about one-fourth. The same fact has been recorded by other observers.[4] Mosso has also noted the fact[5] that there is a change in the type of respiration, the movements during sleep become less diaphragmatic and more largely costal. He furthermore observed that during the waking period the act of inspiration consumed 8-12 of the complete respiratory phase, but during sleep it was prolonged till it occupied 10-12 of the same cycle. The interval between the end of expiration and the commencement of inspiration was also obliterated by sleep. Notwithstanding this relative increase of inspiratory motion, the quantity of air that passes through the lungs is considerably reduced by reason of the diminished action of the diaphragm. A corresponding reduction of the gaseous exchanges between the blood and the external air has been determined by the experiments of Pettenkofer and Voit, Boussingault, Lewin, and other equally competent observers.[6]