Page:The World as Will and Idea - Schopenhauer, tr. Haldane and Kemp - Volume 2.djvu/475

Rh the brain, as of all the parts, takes place, sleep is short; and finally why excessive sleep produces a certain dulness of consciousness, the consequence of a certain hypertrophy of the brain, which in the case of habitual excess of sleep may become permanent and produce imbecility: (noxæ est etiam multus somnus), Od. 15, 394. The need of sleep is therefore directly proportionate to the intensity of the brain-life, thus to the clearness of the consciousness. Those animals whose brain-life is weak and dull sleep little and lightly; for example, reptiles and fishes: and here I must remind the reader that the winter sleep is sleep almost only in name, for it is not an inaction of the brain alone, but of the whole organism, thus a kind of apparent death. Animals of considerable intelligence sleep deeply and long. Men also require more sleep the more developed, both as regards quantity and quality, and the more active their brain is. Montaigne relates of himself that he had always been a long sleeper, that he had passed a large part of his life in sleeping, and at an advanced age still slept from eight to nine hours at a time (Liv. iii., chap. 13). Descartes also is reported to have slept a great deal (Baillet, Vie de Descartes, 1693, p. 288). Kant allowed himself seven hours for sleep, but it was so hard for him to do with this that he ordered his servant to force him against his will, and without listening to his remonstrances, to get up at the set time (Jachmann, Immanuel Kant, p. 162). For the more completely awake a man is, i.e., the clearer and more lively his consciousness, the greater for him is the necessity of sleep, thus the deeper and longer he sleeps. Accordingly much thinking or hard brain-work increases the need of sleep. That sustained muscular exertion also makes us sleepy is to be explained from the fact that in this the brain continuously, by means of the medulla oblongata, the spinal marrow, and the motor nerves, imparts the stimulus to the muscles which affects their irritability, and in this way it exhausts its strength.