A Treatise on diseases of the nervous system / By William A. Hammond.

  • William Alexander Hammond
Date:
1871
Catalogue details

Licence: Public Domain Mark

Credit: A Treatise on diseases of the nervous system / By William A. Hammond. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    Thus, it is an illusion if a person on looking at an object sees two images. This result is clue to some cause destroying the parallelism of the visual axes, and may be produced by a tumor of the orbit or by paralysis of one or the other of the ocular muscles. Even in such a case, if the paralysis were due to central lesion, the higher ganglia of the brain might escape implication. Illusions are often excited by emotional disturbance, and are then probably directly due to some disturbance of the cerebral circulation. The false perceptions called hallucinations are of more importance than illusions, in the symj)tomatology of insanity in general. In the purely perceptional form of mental aberration they are also exceedingly interesting, and are very often trouble- some symptoms. Thus, a gentleman, who had overworked himself in financial business, was subject to hallucinations of hearing, which, however, did not in the least impose on his intellect. As he walked through the streets to his place of business, he heard a voice continually whispering to him, Take care—take care! So strong was the impression made, that he often involuntarily turned round to see who was speaking to him. In another case, a gentleman saw im- ages of various kinds as soon as his head touched the pil- low, though they were never present when he was standing or sitting. The case of Nicolai, the German bookseller of the last century, is well known as a remarkable example, and othei-s are afforded in the cases of Jerome Cardan, Pascal, and many other noted personages. Like illusions,' the immediate cause of hallucinations is generally derangement of the cerebral circulation, either as regards quantity or quality. As is well known, they are frequently produced by alco- ' For a fuller account of the subjects of illusions and hallucinations, the reader is referred to the author's works on Sleep and its Derangements : J. B. Lippincott & Co., Philadel])hia ; and the Physics and Physiology of Spiritualism: D. Appleton & Co., New York.