Autoscopy is an abnormal power of observing and representing the anatomical and functional state of the subjects own internal organs. If the representation is external, in a hallucinatory form, it is termed external autoscopy; if the observation is direct, it is termed internal autoscopy. The phenomenon, which occurs most clearly in the hypnotic state, is analogous, Sollier suggests, to the power shown in premonitory dreams, by which the disturbance of internal organs becomes definitely clear to sleeping consciousness before it is perceived by waking consciousness. Autoscopy was vaguely known to the ancient magnetisers; more recently attention was called to it by Féré; it has been most thoroughly studied by Sollier and Comar.