A hallucination, although recognized and appreciated as such by the person who is the subject of it, may, by its vividness and long continuance, produce so depressing an influence on the mind as to be the cause of suicide. "I knew," says Wigan, "a very intelligent and amiable man, who had the power of this placing before his own eyes _himself_, and often laughed heartily at _his double_, who always seemed to laugh in turn. This was long a subject of amusement and joke; but the ultimate result was lamentable. He became gradually convinced that he was haunted by himself, or (to violate grammar for the sake of clearly expressing his idea) by his _self_. This other self would argue with him pertinaciously, and, to his great mortification, sometimes refute him, which, as he was very proud of his logical powers, humiliated him exceedingly. He was eccentric, but was never placed in confinement or subjected to the slightest restraint. At length, worn out by the annoyance, he deliberately resolved not to enter on another year of existence--paid all his debts--wrapped up in separate papers the amount of the weekly demands--waited pistol in hand, the night of the 31st of December, and as the clock struck twelve, fired it into his mouth." We read in Dr. de Boismont's very able treatise on Hallucinations (translated by Hulme):--"All mental labour, by over-exciting the brain, is liable to give rise to hallucinations. We have known many persons, and amongst others a medical man, who, when it was night, distinctly heard voices calling to them; some would stop to reply, or would go to the door, believing they heard the bell ring. This disposition seems to us not uncommon in persons who are in the habit of talking aloud to themselves."