Extraordinary noises, and revelations from the other world, belong to hallucinations of hearing.

The voices may be very near, or heard at a distance, and in different directions, or they may consist of noises of various kinds.

Hallucinations sometimes occur only on one side. The hallucinated hear with but one ear, or see with but one eye; these are the double hallucinations (hallucinations dedoublees) of Mr. Michea.

Hallucinations of hearing, instead of being external, become internal.

The loss of the senses is no obstacle to the manifestation of hallucinations.

Hallucinations of sight are very usual with persons of sound mind, whilst those of hearing are much more common with the deranged.

Amongst the intellectual phenomena of hallucinations of sight, may be noticed the reproduction for a greater or less time of an object always the same, which afterwards assumes a great variety of changes.

Hallucinations of sight have often an intimate relation with actual preoccupation of mind; at other times, they are the reproduction of vivid anterior sensations.

Hallucinations of sight are generally formed by the most habitual ideas and occupations. In general, the image is entire, but sometimes a part only is developed; for example, half of a body, a head, or an eye. It is probable that this difference in the representative sign depends on the mode of conception. Thus, when an idea has caused a deep impression, the image is reproduced entire, whilst the individual sees it imperfectly, or mistily, when the impression has been weak. Perhaps to this cause may be attributed the manner in which a number of the deranged speak of their hallucinations; they have said, they have insulted me, and no other explanation can be obtained.

The sensorial phenomena of hallucinations of sight form a more interesting study than those of hearing. From their commencement, they have emotion, and varieties of size, and form.

Hallucinations, in general, appear suddenly; they may disappear in like manner, remain a certain time, or decrease gradually. In some cases, hallucinations are developed at the same time with derangement, and cease with it.

Hallucinations occur generally in the night, or, at least, have more intensity at that period. They are also frequently noticed during the day, and in numerous cases continue both night and day. Closing the eyes often causes hallucinations to disappear; in some circumstances, the contrary effect is produced.

The images are opposite, and follow the directions of the eyes; they may be at the side; and are at times intercepted by opaque bodies. In general, fantastic images cover external objects, and conceal them from the sight.

Hallucinations of smel], taste, and touch are simpler and more rare than those of hearing and of sight; they reproduce almost exclusively sensorial impression, and are, moreover, extremely difficult to distinguish from illusions. To hallucinations of this nature must be referred those pestilential emanations from individuals, destroying everything around them.

False perceptions of general sensibility, and especially those of hypochondriacs, may originally arise from the brain, and be only secondarily conveyed to an organ.

Hallucinations are rarely confined to one sense, although one generally predominates. It would appear, according to Mons. Pressat, that false sensations succeed each other in regular order.

Psychical hallucinations, which are almost exclusively constituted of the perceptions of hearing, comprise intellectual visions, and the locutions and interior voices of mystics, which leave no sensorial impression on the mind. The hallucinists of this class, converse mentally, by thought, by idea, mind to mind, hear voices in the epigastrium, and receive communications by means of a sixth sense.

Independently of hallucinations adapted to each sense, there are some common to the whole group.

Hallucinations may exist, for a length of time, without affecting the reason; but the struggle which the sufferer undergoes generally terminates by imparting a strangeness to his conduct.

The steady belief of the hallucinated in the reality of their false sensations, explains the indomitable constancy of sorcerers in the midst of tortures. (Doubtless, a more or less decided anesthetic must be added.)

Amongst the reasons for this conviction may be ranked the correct judgment of the sufferer in matters foreign to their delirium. Some, however, recognize the falsity of their sensations.

The nature of hallucinations is influenced by the different forms of insanity.

All men may have hallucinations, the most exalted as well as the feeblest minds.

The influence of hallucinations may lead to very serious results.

Circulatory and digestive functions, sleep and the secretions, evince alterations.

Certain periods are more favorable to the production of hallucinations; such as the transition from sleep to waking, and from waking to sleep, evening, and night. Many hallucinations occur indifferently, however, by night or day.

In the hallucinations of dreams, all the false sensations may be felt which are observed in waking.

The labor of thought may be continued in dreams, which explains many curious cases which have been described.

The accounts given by sorcerers of the mysteries of the Sabbath, were only hallucinations occurring in dreams.

One peculiarity noticed in some deranged persons is, that their conduct during the day is guided by the false sensorial impressions of the night.

The hallucinations of somnambulism offer a great resemblance to those of dreams; they may also occasion very reprehensible acts.

Illusions may exhibit all the sensorial and intellectual phenomena of hallucinations, which they frequently accompany; their essential characteristic is the transformation of external bodies, into fanciful conceptions. Deranged persons may also believe themselves to be the metamorphosed object.