INTRODUCTION
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duced by such purely physiological mechanisms, I cannot do better than summarize the interesting articles of Mr . Lydiard H. Horton, which appeared in the Journal of Abnormal Psychology (April, 1918 ; June, 1918 ; August, 1919), in which he attempted to prove this fact-that such illusions of levitation may be so produced-even without sleep ! He induced a number of experimental subjects to lie upon a bed or couch, and relax completely . Upon the degree of relaxation thus attained depends the success of the experiment . If the patient can induce this complete relaxation of the muscular system without falling asleep, he will often experience an " illusion of levitation." " Out of the thirty subjects who relaxed completely, and of the twenty or so who retained consciousness after they had completely relaxed, eight of them reported illusions of levitation ." The following are typical experiences of this nature " One of them jumped out of the chair and was afraid to continue the experiment, so realistic was his apperception of a soaring motion . " Another, this time a woman, gripped the chair in the momentary belief that she was floating away ; two others reported that they felt ' caught up ' by a wave, but that their reason reassured them at the time . " One other enjoyed the sensation so much that he took it as a matter of course, and supposed it was part of the ' treatment .' One other said that if his head had been as light as his body he would surely have floated away . He reported himself ` just floating away,' the sensation being overwhelmingly real . . . ." Mr. Horton attempts to account for all such cases as follows " The mechanism underlying the flying dream and the levitation illusion is attributed, mainly, to the functions of the adrenal-sympathetic nervous system . . . . The genesis of the illusion of levitation does not come from the diminution of tactile sensations . Whether due entirely to an inhibition in the course of the pressure sense tracts (deep sensibility, I mean), or merely to lessening of actual muscle pressure, is a question . I think the latter is a great factor, but that the sensory ' inhibition ' is real too . . . . This of itself does not become the adequate or efficient basis of the illusion of levitation till the vaso-motor relaxation supervenes . Out of the combination there arises the bodily ' stimulus ' (negative in this case) which becomes the foundation of the illusion of soaring . . . ." This attempted explanation, it will be observed, differs essentially from that offered by Horace G . Hutchinson (in his Dreams and their Meanings) and also that of Havelock Ellis (in his World of Dreams) which is that " flying dreams " are best explained by a combination of respiratory sensations together with cutaneous anaesthesia . It is quite possible that some such explanation may ultimately be found for, and will adequately explain, many .ordinary flying dreams ; but it must be emphasized emphatically that such dreams are quite different from clean-cut instances of " projection," and that any