Visual creations undergo motions, changes of dimension, and transformations of form. Thus objects which appear fixed, begin to move and increase indefinitely, until they vanish into distance. Some, on the contrary, gradually shrink until they appear to sink into the earth.

Mr. Bayle mentions an old custom-house officer, who was daily tormented, at a certain hour, by a very singular vision; all at once he would perceive a spider suspended from the middle of the ceiling. He would see it increase in size, until it completely filled the room, which he was obliged to leave, in order to avoid being stifled by this horrible and gigantic animal. He recognized an optical delusion, but could not surmount the horror with which it inspired him.

Hallucination, most usually, appears suddenly; it may disappear in like manner or persist for a certain time. "A lady," says Mathey, "on returning home one evening, saw a man in her room, who fled and disappeared through a closed door." The case of Nicolai, already described, contains curious details of the gradual disappearance of the images. The figures began to move more slowly, they then became paler, then vapory, and, finally, dissolved into air. The spectre seen by Spinosa, in his retreat at Rhinbourg, disappeared thus gradually, its colors growing weaker around the head of the philosopher.† The duration of false visual sensations varies considerably. In some cases it only lasts a few minutes, whilst in others the same image has been visible for twenty-four hours or longer. Hallucinations may supervene, almost at the same time, with general delirium, and also cease with it. This disposition, according to M. Lelut, occurs principally with young subjects, of a sanguine temperament and a lively and excitable disposition.

* Theologians have termed apparition a false perception of an object vaguely known; and vision that in which the object is clearly manifested. - Le Cardinal Bona, Da Discernement des Esprits. trad. Franc, p. 675.

† Opera Posthuma, epist. xxx., Petro Balling, pp. 471-472.

Although night, darkness, and silence are favorable to the production of visions, certain individuals have them indifferently by day or night. Objects may disappear on closing the eyes, and appear again on reopening them. With some exceptions, visions only occur during the day, and darkness, far from favoring them, makes them, on the contrary, disappear. But there are also some in whom they occur with eyes either open or closed.

The images which appear to the hallucinists usually confront them, but in some instances they are by their sides. The distance at which they are seen varies curiously. The skeleton head mentioned by Sir Walter Scott, appeared at the foot of the bed.

Sometimes the position of the image changes with the direction of the sight. The physiologist Bostock says that apparitions always follow the movement of the eyes. Many cases seem to prove that the intervention of an opaque body may conceal the fancied image. The celebrated English artist, Martin, saw, it is said, beforehand, and by a real hallucination, the pictures whose plan and composition he had not yet even contemplated.

Science offers many analogous cases; but it is more usual to find fantastic images conceal external objects from the sight of the diseased person. The German physiologist, Gruthuisen, says he is perfectly sure that floating images entirely hid the furniture of the room from his sight.

Hallucinations of sight occur less frequently with the blind than do those of hearing with the deaf. Nevertheless, science is in possession of several examples, and in our own practice we have noticed three. We have mentioned that of the celebrated Niebuhr, who described to his friends all the various scenes which he had formerly seen in his travels; whilst he spoke, they rose up before him in all the coloring, animation, and 6plendor of nature. An old lady, of eighty-two years, saw a considerable number of persons enter her room daily; she had the door and window opened in order that they might pass out. In the private hospital of my daughter, Madame Rivet, is a person blind, deaf, and dumb, who both sees and hears.

Hallucinations of smell, taste, and touch are simpler than those which we have just examined. They are only the reproduction of a sensorial impression. It is very difficult to distinguish them from illusions.

Some individuals who experience hallucinations of smell, think they inhale the most exquisite perfumes; others, again, complain that they are poisoned by mephitic and pestilential odors. The appearance of holy personages fills the room with the most delicious scents, whilst that of demons leaves sulphuric and noisome exhalations. A madman, who had sinned against good morals, complained that the devil had enveloped him in a cloud of sulphur. M. Baillarger knew a lady who was continually distressed by an infectious odor which she believed to emanate from herself. One day that Esquirol invited her to walk in the garden, she refused, fearing, as she said, that all the plants would be killed by the scent from her person.

To these hallucinations, and this species of delirium, may be referred what Don Calmet relates of certain men, "who damaged all they looked upon, even to the breasts of the nurses, whose milk they dried up; the plants, flowers, and leaves of the trees, which fell off and died on their approach; so that they dared not enter any place without first giving notice, in order that children, nurses, young animals, and everything which their looks could infect, should be removed."* In proportion as we progress in the study of this singular affection, do we account for a host of historical documents, which the ignorant skepticism of the eighteenth century has ranked amongst fables.

Hallucinations of taste are likewise rare; they are generally observed at the commencement of insanity, and during its most active period. Cases in which they exist alone, in a chronic state are very unusual. Such persons believe they are partaking of excellent viands and drinking delicious wines, although they have really nothing. Others complain of having detestable food, tasting of verdigris. Illusions of taste are more frequent.