Licence: Public Domain Mark
Credit: On going to sleep. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![SOMNAMBULISM. having a strong desire to sleep, but to be kept awake by the feelings in the right side of his head. But perhaps the most striking illustrations of a partial in- terception of the blood current into the brain are those comprising the more usual forms of somnambulism ana double consciousness. The phenomena usually observed in somnambulism are some awakening of thought, consciousness, and will, recovered tactile sensibility, control over the muscles of the body and limbs, an open eye and dilated pupil ] but obscure vision or blindness, dulness of hear- ing or deafness, and withal, after relapsing into sleep and complete awakening, no recollection of the purposes or occurrences of the somnambulistic state. In addition to these, Dr. Hughlings Jackson once found by the ophthalmoscope that, as in sleep, the retina of a somnam- bulist was pale* All these phenomena appear intelli- gible on the supposition that the parts in the area of the carotid circulation continue asleep, while those supplied from the basilar artery awake ; that, in fact, the somnambulism thus characterised is due to a renewed dilatation of the basilar artery alone. In the first place, it appears to be clear from the entire absence of memory in the waking state as to what passed during the somnambulism, that some portion of the brain was wholly unoccupied with the thoughts and * ‘ Observations on Defects of Sight in Brain Disease, and Ophthal- moscopic Examination during Sleep,’ by J. Hughlings Jackson, M.D., 1863, p. 15. E](https://iiif.wellcomecollection.org/image/b22361261_0059.jp2/full/800%2C/0/default.jpg)
