Out of slumber proceeds each fresh arousal and initiation of waking activities. What other activities may in slumber be aroused and initiated the evidence to be set forth in this chapter should help us to say. To some extent at least the abeyance of the supraliminal life must be the liberation of the subliminal. To some extent the obscuration of the noonday glare of man's waking consciousness must reveal the far-reaching faint corona of his unsuspected and impalpable powers. Entering, then, upon a review of sleeping faculty, thus inevitably imperfect, we may best begin from the red end of our spectrum of consciousness;--the red end which represents the deepest power which waking effort can exert upon our physical organism. Our survey of the efficacy of sleep, indeed, must make its beginning _beyond_ that limit. For assuredly in sleep some agency is at work which far surpasses waking efficacy in this respect. It is a fully admitted, although an absolutely unexplained fact, that the regenerative quality of healthy sleep is something _sui generis_, which no completeness of waking quiescence can rival or approach. A few moments of sleep--a mere blur across the field of consciousness--will sometimes bring a renovation which hours of lying down in darkness and silence would not yield. A mere bowing of the head on the breast, if consciousness ceases for a second or two, may change a man's outlook on the world. At such moments,--and many persons, like myself, can fully vouch for their reality,--one feels that what has occurred in one's organism,--alteration of blood-pressure, or whatever it be,--has been in some sense discontinuous; that there has been a break in the inward _régime_, amounting to much more than a mere brief ignoring of stimuli from without. The break of consciousness is associated in some way with a potent physiological change. That is to say, even in the case of a moment of ordinary sleep we already note the appearance of that special recuperative energy which is familiar in longer periods of sleep, and which, as we shall presently see, reaches a still higher level in hypnotic trance. This recuperative power, then, lies just beyond the red end of our spectrum of waking faculty. In that obscure region we note only added power; an increased control over organic functions at the foundation of bodily life. But when we pass on within the limits of our spectrum of waking consciousness;--when we come to control over voluntary muscles, or to sensory capacity, we find that our comparison between sleeping and waking faculty is no longer a simple one. On the one hand, there is of course a general blank and abeyance of control over the realm of waking energies;--or in partial sleep a mere fantastic parody of those energies in incoherent dream. On the other hand, we find that sleep is capable of strange developments,--and that night can sometimes suddenly outdo the most complex achievements of day.