A natural and healthy, but temporary and periodical, suspension of the functions of the organs of sense, as well as of those of the voluntary and rational soul; that state of the animal in which there is a lessened acuteness of sensory perception, a confusion of ideas, and a loss of mental control, followed by a more or less unconscious state. A man that waketh of his sleep. O sleep, thou ape of death. (Shak)
Sleep is attended by a relaxation of the muscles, and the absence of voluntary activity for any rational objects or purpose. The pulse is slower, the respiratory movements fewer in number but more profound, and there is less blood in the cerebral vessels. It is susceptible of greater or less intensity or completeness in its control of the powers.
Origin: AS. Slp; akin to OFries. Slp, OS. Slap, D. Slaap, OHG. Slaf, G. Schlaf, Goth. Slps. See Sleep.