And not only this. His hallucinations are in most cases elaborate products--complex images which must have needed intelligence to fashion them--although the process of their fashioning is hidden from our view. In this respect they resemble the inspirations of genius. For here we find again just what we found in those inspirations--the uprush of a complex intellectual product, performed beneath the threshold, and projected ready-made into ordinary consciousness. The uprushing stream of intelligence, indeed, in the man of genius flowed habitually in conformity with the superficial stream. Only rarely does the great conception intrude itself upon him with such vigour and such untimeliness as to bring confusion and incoherence into his ordinary life. But in the case of these induced hallucinations the incongruity between the two streams of intelligence is much more marked. When a subject, for instance, is trying to keep down some post-hypnotic hallucinatory suggestion, one can watch the smooth surface of the supraliminal river disturbed by that suggestion as though by jets of steam from below, which sometimes merely break in bubbles, but sometimes force themselves up bodily through the superficial film. It is by considering hallucinations in this generalised manner and among these analogies, that we can best realise their absence of necessary connection with any bodily degeneration or disease. Often, of course, they accompany disease; but that is only to say that the central sensory tracts, like any other part of the organism, are capable of morbid as well as of healthful stimulus. Taken in itself, the mere fact of the quasi-externalisation of a centrally initiated image indicates strong central stimulation, and absolutely nothing more. There is no physiological law whatever which can tell us what degree of vividness our central pictures may assume consistently with health--short of the point where they get to be so indistinguishable from external preceptions that, as in madness, they interfere with the rational conduct of life. That point no well-attested case of veridical hallucinations, so far as my knowledge goes, has yet approached. It was, of course, natural that in the study of these phantasms, as elsewhere, the therapeutic interest should have preceded the psychological, but in the newer practical study of _eugenics_--the study which aims at improving the human organism, instead of merely conserving it--experimental psychology is indispensable, and one branch of this is the experimental study of mental visions. Let us consider whether, apart from such a rare and startling incident as an actual hallucination, there is any previous indication of a habit of receiving, or a power of summoning, pictures from a subliminal store-house? Any self-suggestion, conscious or unconscious, which places before the supraliminal intelligence visual images apparently matured elsewhere?