[Footnote 56: Although I reached this conclusion independently, as a result of the analysis of dream experiences, I find that it was set forth at a much earlier period by Wundt. 'Men are accustomed to regard most of the phantasms of dreams as hallucinations,' he writes (_Grundzüge der Physiologischer Psychologie_, vol. iii.), 'but most dream representations are apparently illusions, initiated by the slight sensory impressions which are never extinguished in sleep.' Weygandt, in his brief but excellent book, _Entstehung der Traäme_, fully adopts this view, although I scarcely think he is always successful in his attempts to demonstrate it by his own dreams; such demonstration is necessarily often difficult or impossible because, apart from the dream itself, we seldom know what sensory impressions are persisting in our sleep. C. M. Giessler (_Die Physiologische Beziehungen der Traumvorgänge_, 1896, p. 2), who also proceeds from Wundt, likewise regards dreams as in general the more or less orderly and successive revival of psychic vestiges of waking life, conditioned by inner or outer excitations. Tissié (in _Les Rêves_, 1898), again, declares that 'dreams of purely psychic origin do not exist,' and Beaunis (_American Journal of Psychology_, July-October 1903) also believes that all dreams need an internal or external stimulus from the organism.] [Footnote 57: Thus W. S. Monroe ('Mental Elements of Dreams,' _Journal of Philosophy_, 23rd November 1905) found that in nearly three hundred dreams of fifty-five women students of the Westfield Normal College (Massachusetts), visual imagery appeared in sixty-seven per cent. dreams, auditory in twenty-six per cent., tactile in eight per cent., motor in five per cent., olfactory in a little over one per cent., and gustatory in rather under one per cent. In the results of observation recorded by Sarah Weed and Florence Hallam (_American Journal of Psychology_, April 1896) the sensory imagery appears in the same order of frequency and approximately in the same proportions.] [Footnote 58: In another case, a sensation of irritation in the palm led to a dream of being scratched by a cat. Guthrie mentions (_Clinical Journal_, 7th June 1899) that as a child he used to dream of being tortured by savages by being slowly tickled under the arms when unable to move; he sweated much at night, and considers that the tickling thus caused was the source of the dreams.] [Footnote 59: The corresponding sensation of heat can also, of course, be experienced in sleep, alike whether the stimulus comes from the brain or the skin. Thus I dreamed that, not knowing whether some water was hot or cold, I put my finger into it and felt it to be distinctly hot.]