The following observations are from Dr Rush, found in his Treatise on Diseases of the Mind. 'By this term, (Illusions) I mean that disease, in which false perceptions take place in the ears and eyes in the waking state, from a morbid affection of the brain, or of the sense which is the seat of the illusion. It may be considered as a waking dream. Persons affected with it fancy they hear voices, or see objects that do not exist. These false perceptions are said, by superstitious people, to be premonitions of death. They sometimes indicate either the forming state, or the actual existence of disease, which being seated most commonly in a highly vital part of the body, that is, in the brain, now and then ends in death, and thus administers support to superstition. They depend, like false perception in madness, upon motion being excited in a part of the ear or the eye, which does not vibrate with the impression made upon it, but communicates it to a part upon which the impression of the noise heard, or of the person seen, was formerly made, and hence the one becomes audible, and the other visible. 'The deception, when made upon the ears, consists most commonly in hearing our own names, and for this obvious reason; we are accustomed to hear them pronounced more frequently than any other words, and hence the part of the ear, which vibrates with the sound of our names, moves more promptly, from habit, than any other part of it. For the same reason the deception, when made upon the eyes, consists in seeing our own persons, or the persons of our intimate friends, whether living or dead, oftener than any other people. The part upon the retina, from which those images are reflected, move more promptly, from habit, than any other of that part of the organ of vision. 'The voice which is supposed to be heard, and the objects which are supposed to be seen, are never heard nor seen by two persons, even when they are close to each other. This proves them both to be the effect of disease in the single person who hears, or sees, the supposed voice or object.' Dr Rush has recorded numerous instances of partial mental derangement from hypochondriasis, chiefly from his own knowledge, such as the following. A sea captain believed that he had a wolf in his liver; others that they are converted into an animal of another species, such as a goose, a dog, a cat, a hare, a cow, and the like. One imagined that he was once a calf, and mentions the name of the butcher that killed him, and the stall in the Philadelphia market, on which his flesh was sold, previously to his animating his present body. One believed that he had no soul. Another that he is transformed into a plant, and insisted on being watered in common with all the plants around him in the garden. Another that his body was transformed into glass. The celebrated Cowper suffered much anguish from complaints of a similar nature, arising from hypochondriac affection.