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.
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.
The degree of acuteness, not of the visualising faculty alone, but of all the senses in dream, is a subject for direct observation, and even—for persons who can at all control their dreams—for direct experiment. Some correspondents report a considerable apparent accession of sensory power in dream. Others again speak of the increased vividness of dramatic conception, or of what has been called in a hypnotic subject "objectivation of types." "In each of these dreams," writes one lady, "I was a man;—in one of them a low brute, in the other a dipsomaniac. I never had the slightest conception of how such persons felt or thought until these experiences." Another correspondent speaks of dreaming two disconnected dreams—one emotional and one geometrical—simultaneously, and of consequent sense of confusion and fatigue.
The "Chapter on Dreams," in R. L. Stevenson's volume, Across the Plains (already referred to in the last chapter), contains a description of the most successful dream-experiments thus far recorded. By self-suggestion before sleep Stevenson could secure a visual and dramatic intensity of dream-representation which furnished him with the motives for some of his most striking romances. His account, written with admirable psychological insight, is indispensable to students of this subject. I am mentioning these well-known phenomena, as the reader will understand, with a somewhat novel purpose—to show, namely, that the internal sensory perceptions or imaginative faculty of sleep may exceed that of vigilance in something the same way as the recuperative agency of sleep surpasses the vis medicatrix of waking hours.
I pass on to a less frequent phenomenon, which shows us at once intense imagination during sleep, and a lasting imprint left by these imaginations upon the waking organism;—an unintended self-suggestion which we may compare with Stevenson's voluntary self-suggestion mentioned just above.
The permanent result of a dream, I say, is sometimes such as to show that the dream has not been a mere superficial confusion of past waking experiences, but has had an unexplained potency of its own—drawn, like the potency of hypnotic suggestion, from some depth in our being which the waking self cannot reach. Two main classes of this kind are conspicuous enough to be easily recognised—those, namely, where the dream has led to a "conversion" or marked religious change, and those where it has been the starting-point of an "insistent idea" or of a fit of actual insanity.[40] The dreams which convert, reform, change character and creed, have of course a primâ facie claim to be considered as something other than ordinary dreams; and their discussion may be deferred till a later stage of our inquiry. Those, on the other hand, which suddenly generate an insistent idea of an irrational type are closely and obviously analogous to post-hypnotic self-suggestions, which the self that inspired them cannot be induced to countermand. Such is the dream related by M. Taine,[41] where a gendarme, impressed by an execution at which he has assisted, dreams that he himself is to be guillotined, and is afterwards so influenced by the dream that he attempts suicide. Several cases of this kind have been collected by Dr. Faure;[42] and Dr. Tissié, in his interesting little work, Les Rêves, has added some curious instances from his own observation.
A striking illustration may be drawn from the following incident in the story of Krafft-Ebing's patient,[43] Ilma S., the genuineness of whose stigmata seems proved by that physician's care in observation, and by the painfulness of certain experiments performed upon her by students as practical jokes and against her will:—
May 6th, 1888.—The patient is disturbed to-day. She complains to the sister of severe pain under the left breast, thinks that the professor has burnt her in the night, and begs the sister to obtain a retreat for her in a convent, where she will be secure against such attacks. The sister's refusal causes a hystero-epileptic attack. [At length, in the hypnotic trance] the patient gives the following explanation of the origin of the pain: "Last night an old man came to me; he looked like a priest and came in company with a Sister of Charity, on whose collet there was a large golden B. I was afraid of her. The old man was amiable and friendly. He dipped a pen in the sister's pocket, and with it wrote a W and B on my skin under the left breast. Once he dipped his pen badly and made a blot in the middle of the figure. This spot and the B pain me severely, but the W does not. The man explained the W as meaning that I should go to the M church and confess at the W confessional."
After this account the patient cried out and said, "There stands the man again. Now he has chains on his hands."
When the patient woke into ordinary life she was suffering pain in the place indicated, where there were "superficial losses of substance, penetrating to the corium, which have a resemblance to a reversed W and B," with "a hyperæmic raised spot between the two." Nowhere in this peculiar neurotrophic alteration of the skin, which is identical with those previously produced experimentally, are there traces of inflammation. The pain and the memory of the dream were removed by the doctor's suggestion; but the dream self-suggestion to confess at the M church persisted; and the patient, without knowing why, did actually go and confess to the priest of her vision.
In this last case we have a dream playing the part of a powerful post-hypnotic suggestion. The meaning of this vague term "suggestion" we shall have to discuss in a later chapter. It is enough to notice here the great power of a subliminal suggestion which can make an impression so much stronger not only than the usual evanescent touch of dream, but than the actual experiences of waking day.
But this case may also serve to lead us on to further reflections as to the connection between dream-memory and hypnotic memory, a connection which points, as we shall presently see, towards the existence of some subliminal continuity of memory, lying deeper down than the evocable memory of common life—the stock of conscious reminiscences on which we can draw at will.
With regard to memory, as with regard to sensation, we seem in waking life to be dealing with a selection made for purposes of earthly use. From the pre-conscious unselective memory which depends on the mere organisation of living matter, it is the task of consciousness, as it dawns in each higher organism, to make its own appropriate selection and to develop into distinctness certain helpful lines of reminiscence. The question of self-preservation—What must I needs be aware of in order to escape my foes?—involves the question, What must I needs remember in order to act upon the facts of which I am aware? The selected currents of memory follow the selected avenues of sensation; what by disuse I lose the power of noticing at the time, I also lose the power of recalling afterwards.
For simpler organisms this rule may perhaps suffice. Man needs a more complex formula. For it may happen, as we have already seen, that two or more phases of personality in one man may each select from the mass of potential reminiscences a special group of memories of its own. These special groups, moreover, may bear to one another all kinds of relations; one may include another, or they may alternate and may be apparently co-exclusive.
From these dissociations and alternations of memory there will be many lessons to learn. The lesson which here presents itself is not the least important. What is the relation of the sleeping state to these dissociated, these parallel or concentric memories? Is it the case that when one memory includes another it is the waking memory—as one might expect from that state's