We find in Abercrombie's work the case of a gentleman "who has been all his life affected by the appearance of spectral figures. To such an extent does this peculiarity exist, that, if he meets a friend in the street, he cannot at first satisfy himself whether he really sees the individual or a spectral figure. By close attention he can remark a difference between them, in the outline of the real figure being more distinctly defined than that of the spectral; but in general he takes means for correcting his visual impression by touching the figure, or by listening to the sound of his footsteps. He has also the power of calling up spectral figures at his will, by directing his attention steadily to the conception of his own mind; and this may consist either of a figure or a scene which he has seen, or it may be a composition created by his imagination. But, though he has the faculty of producing the illusion he has no power of vanishing it; and, when he has called up any particular spectral figure or scene, he never can say how long it may continue to haunt him. The gentleman is in the prime of life, of sound mind, in good health, and engaged in business. Another of his family has been affected in the same manner, though in a slight degree."
It would be easy to mention many examples of illustrious men who have been subject to hallucinations, without their having in any way influenced their conduct.
Thus, Malebranche declared he heard the voice of God distinctly within him. Descartes, after long confinement, was followed by an invisible person, calling upon him to pursue the search of truth.
Byron occasionally fancied he was visited by a spectre, which he confesses was but the effect of an over-stimulated brain.
Dr. Johnson said that he distinctly heard his mother's voice call "Samuel." This was at a time when she was residing a long way off.
Pope, who suffered much from intestinal disease, one day asked his medical man what the arm was which seemed to come out of the wall.
Goethe positively asserts that he one day saw the exact counterpart of himself coming towards him. The German psychologists give the name of Deuteroscopia to this species of illusion.
[Strange Hallucination.]
On the 25th of November, 1840, Mr. Pearce, the author of several medical works, was tried at the Central Criminal Court for shooting at his wife with intent to murder, and acquitted on the ground of insanity. He entertained the peculiar notion that his wife wished to destroy him, and that she had bribed persons to effect his death in various ways, the principal of which was that his bed was constantly damped or wetted. This idea seems to have haunted him continually. He was shortly after his acquittal taken to Bethlem Hospital. For some time he refused to leave the gallery in which his cell was situated, and go into the airing-ground; in order, as it appeared, that he might watch his cell door to prevent anything "villanous" being done.