404. 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.

Take first the degree of control over the voluntary muscles. In ordinary sleep this is neither possessed nor desired; in nightmare its loss is exaggerated, in quasi-hysterical fashion, into an appalling fear; while in somnambulism, - a kind of new personality developed ad hoc, - the sleeper (as we shall see later on) walks on perilous ridges with steady feet. I have already said that morbid somnambulism bears to sound sleep a relation something like that which hysteria bears to normal life. But between the healthy somnambulist and the subject of nightmare we find from another point of view a contrast resembling that between the man of genius and the hysteric. The somnambulist, like the man of genius, brings into play resources which are beyond ordinary reach. On the other hand, just as in many hysterics certain ordinary powers of movement have lapsed below voluntary control, so also the dreamer who dimly wishes to move a constrained limb is often unable to send thither a sufficient current of motor energy to effect the desired change of position.

That nightmare inability to move, which we thus feel in dream, - " when neither he that fleeth can flee, nor he that pursueth pursue," - that sensation which both Homer and Virgil have selected as the type of paralysing bewilderment,1 - this is just the aboulia of the hysteric; - the condition when it takes a man half-an-hour to put on his hat, or when a woman sits all the morning looking at her knitting, but unable to add a stitch.

"Somnambulism," however, is too vague and undefined a term for our present discussion. It will only be by a comparison with hypnotism, in the next chapter, that we can hope to get some clearer notion of "sleep-waking" states.

405. Let us pass on to consider entencephalic sensory faculty, - "mind's eye" faculty, - as shown in sleep or dream. Here too we shall find the same rule to prevail as with motor faculty. That is to say, on the whole the sensory faculty is of course dimmed and inhibited by sleep; but there are nevertheless indications of a power subsisting as vividly as ever, or with even added acuteness.

There seems, of course, at first sight, something of paradox in expecting hyperæsthesia from somnolence; - vivid sensation from a condition usually described as a progressive dulling or subsidence of one sense after another. And, naturally, it will be in the generation of internal rather than in the perception of external imagery that we may expect to find the closed eye active:

ϐρώtα λαμπρoυ ευ σkótώ vωμώυr' oΦpùiυ.

There is in fact a phenomenon, by no means uncommon, and very conspicuous, which, like many other human phenomena whose interest is really scientific rather than therapeutic, remained unnoticed by science until a very recent date. Baillarger in France and Griesinger in Germany (both about 1845) were among the first to call attention to the vivid images which rise before the internal vision of many persons, between sleep and waking. M. Alfred Maury, the well-known Greek scholar and antiquary, gave to these images a few years later the title of illusions hypnagogiques, and published a remarkable series of observations upon himself. Mr. Galton has further treated of them in his Inquiry into Human Faculty, and cases will be found in Phantasms of the Living, vol. i. pp. 390, 473, etc.

These visions may be hypnopompic as well as hypnagogic; - may appear, that is to say, at the moment when slumber is departing as well as at the moment when it is coming on; - and in either case they are closely related to dreams; the " hypnagogic illusions" or pictures being sometimes repeated in dream (as with Maury), and the hypnopompic pictures consisting generally in the persistence of some dream-image into the first moments of waking. In either case they testify to an intensified power of inward visualisation at a very significant moment; - a moment which is actually or virtually one of sleep, but which yet admits of definite comparison with adjacent moments of waking. We may call the condition one of cerebral or "mind's eye" hyperæsthesia, - an exalted sensibility of special brain-centres in response to those unknown internal stimuli which are always giving rise to similar but fainter inward visions even in broadly waking hours.

1 Iliad, xxii. 199; Æneid, xii. 908.

For those who are already good visualisers such phenomena as these, though striking enough, present no quite unique experience. For bad visualisers, on the other hand, the vividness of these hypnagogic pictures may be absolutely a revelation. For myself, I may say that were it not for an occasional flash of this kind between sleep and waking, I should be unable to conceive what good visualisation really is. The dim, blurred, unstable images which are all that my waking will can summon up are every now and then replaced in a moment of somnolence by a picture - say of a wet hedge in the sun - which seems, to my hurried glance, to be absolutely as clear and brilliant as the object itself could be. The difference is like that between an instantaneous photograph (and in natural colours!) and a dim dissolving view cast by a magic lantern on the point of going out. Many men must have had this experience; and must have been struck with the unguessed reserve of faculty which for a moment was thus revealed.