[64] It is stated by Baillarger (Memoires de l’Academie Royale de Medicine, tom. xii. p. 273, etc.) that while visual hallucinations are more frequent than auditory in healthy life, the reverse relation holds in disease.  At the same time, Griesinger remarks (loc. cit., p. 98) that visual hallucinations are rather more common than auditory in disease also.  This is what we should expect from the number of subjective sensations connected with the peripheral organ of vision.  The greater relative frequency of auditory hallucinations in disease, if made out, would seem to depend on the close connection between articulate sounds and the higher centres of intelligence, which centres are naturally the first to be thrown out of working order.  It is possible, moreover, that auditory hallucinations are quite as common as visual in states of comparative health, though more easily overlooked.  Professor Huxley relates that he is liable to auditory though not to visual hallucinations. (See Elementary Lessons in Physiology, p. 267.)

[65] See Baillarger, Memoires de l’Academie Royale de Medicine, tom. xii. p. 273, et seq.

[66] See Baillarger, Annales Medico-Psychologiques, tom. vi. p. 168 et seq.; also tom. xii. p. 273, et seq. Compare Griesinger, op. cit. In a curious work entitled Du Demon de Socrate (Paris, 1856), M. Lelut seeks to prove that the philosopher’s admonitory voice was an incipient auditory hallucination symptomic of a nascent stage of mental alienation.

[67] This is well brought out by Dr. J. Hughlings Jackson, in the papers in Brain, already referred to.

[68] Friend, vol. i. p. 248.  The story is referred to by Sir W. Scott in his Demonology and Witchcraft.

[69] See E.B.  Tylor, Primitive Culture, ch. xi.; cf. Herbert Spencer, Principles of Sociology, ch. x.

[70] For a fuller account of the different modes of dream-interpretation, see my article “Dream,” in the ninth edition of the Encyclopaedia Britannica.

[71] For a fuller account of the reaction of dreams on waking consciousness, see Paul Radestock, Schlaf und Traum.  The subject is touched on later, under the Illusions of Memory.

[72] For an account of the latest physiological hypotheses as to the proximate cause of sleep, see Radestock, op. cit., appendix.

[73] Plutarch, Locke, and others give instances of people who never dreamt.  Lessing asserted of himself that he never knew what it was to dream.

[74] The error touched on here will be fully dealt with under Illusions of Memory.

[75] For a very full, fair, and thoughtful discussion of this whole question, see Radestock, op. cit., ch. iv.

[76] This may be technically expressed by saying that the liminal intensity (Schwelle) is raised during sleep.