HALLUCINATIONS, are morbid condi tions of mind in which the patient is conscious of a perception without any impression having been made on the external organs of sense. Hallucinations are to be distinguished from de lusions, for in these there are real sensations, though they are erroneously interpreted. All the senses are not equally subject to hallucina tions; the most frequent are those of hearing; next, according to many, come those of sight, smell, touch and taste; and hallucinations of several senses may exist simultaneously in the same individual. They may also be complicated with certain delusions. Often even the hallu cination of one sense is confirmed by the de lusion of another, so that it is neither possible nor necessary always to distinguish hallucina tions from delusions. The simplest form of hallucinations of hearing is the tingling of the ears; but the striking of clocks, the sounds of musical instruments and of the human voice are often heard, and in these instances, as in those of the perturbations of the other senses, there must be a diseased sensorium, though there should be no structural derangement of the nerves. Hallucinations are not confined to those whose mental faculties have been alien ated, but occasionally assail and torment even the sane. The second Earl Grey was haunted by a gory head, but he could dismiss it at will Swedenborg had a similar facultyi and Berna dotte, king of Sweden, was besieged in his rides by a woman in a red cloak, being perfectly conscious of the hallucination under which he labored. Lord Brougham proposed that the
existence of hallucinations should be established as an authoritative test for the existence of in sanity; but, as will have been seen, this would be no test at all. The proportion of the hallu cinations of the various senses has been by some tabulated thus:— hearing, 49; vision, 48; taste, 8; touch, 3; smell, I. All are more fre quent in mania than in monomania, and in mania errors of vision are more numerous than those of hearing. There is a growing convic tion that many so-called hallucinations and de lusions are not really such, but due to an ab normal ability of the sufferer to sense vibra tions far above the normal. The study of clair voyance and clairaudience indicates that a considerable number of individuals do sense things above the mass of mankind. A study of theosophy and the theory of the astral plane is very interesting in this , connection. Consult Parish, 'Hallucinations and Illusions) (1901) ; Podmore, 'Studies in Psychological Research) (1897). See APPARITIONS; DREAMS ; GHOSTS; INSANITY.