Hallucinations appear sometimes to affect strange forms; but on careful examination, their elements are found to have been imbibed from books, pictures, traditions, etc. Thus, in the Middle Ages, the figure of the devil was borrowed from the prevailing architecture of the time, whose fantastic compositions formed extraordinary ornaments in their Catholic churches; witness the Abbey of St. Martin de Boscherville, near Rouen.

Hallucinations may be derived from objects long since observed and subjects long since forgotten, recalled to the memory by some unconscious cause, often by the association of ideas; thus it is true that, in the great majority of cases, hallucinations are only reminiscences or creations of known objects. Sometimes, however, it is impossible to discover any connection between these false sensations, and occupations thoughts and works. Nicolai and Bostock declare that they could not trace any foundation for their visions. Cardan says that he several times had visions of suits of armor, although it was an object entirely unknown to him.

Hallucinations have not always the character of a fixed idea, or a dominant passion; they are sometimes only the reproduction of recollections and of objects which had impressed the senses. The delirium then assumes a remarkable versatility, both in conversation and action. This is also noticed in some kinds of mania and in febrile delirium. In other circumstances, after having commenced under a simple form, or having only assumed the hallucinations at the close of a certain time, or gradually, they become general, irregular, and attached at the same time to several delirious conceptions.

It may happen that the deranged persons imagine the voices which they hear to come from without, and M. Baillarger observes this to be most commonly the case. Very often, too, the interlocutors are designated by the pronouns he, she, them, and the particle they. When the patients are questioned as to whom these vague denominations apply to, they cannot give any definite answer. When illusions are added to these errors, the patients usually attribute them to those persons who are about them. Far from considering the words addressed to them as a product of their own minds, they attribute them to others; thus they are spoken to in the second person. Their minds embrace as it were two kinds of thought, the one which they know belongs to themselves, the other which they attribute to strangers; this is the fact of intellectual duality noticed in the inspired. These voices may express themselves in the third person, and reveal to them plots contrived against them.

Hallucinations of hearing sustain the for and against, and reflect the strifes of conscience; there are two voices, the one urging to good, the other to evil.

This internal combat occurs also in a state of sanity. In fact, it is not unusual to be harassed between two opposite influences, one of which counsels the adoption of a certain course, and the other opposes it.

"Some hypochondriacs," says Mons. Falret, "suffer indescribable anxiety; they conceive that all manner of precautions are taken to prevent them from committing suicide, whilst secretly the means for effecting it are pointed out. These patients look repulsive and gloomy; despair is painted in all their features; their skin is cadaverous; their deeply-sunk eyes are yellow and bloodshot. Cephalalgia exists more or less, usually confined to the forehead, and particularly to the root of the nose. They have a sense of beating within the head; are wakeful, or, if they sleep, have troubled dreams and see fantastic apparitions."

This psychological characteristic demands the attention of the student. It would appear that the same individual has two different beings, the one the principle of good, the other of evil; it is the strife between the good and bad angels. We have related the case of a female who was urged to suicide, by hearing the most disagreeable, painful, and frightful things said to her, and who, at the moment of abandoning herself to despair, felt strengthened and consoled; like the scales of a balance, each rising and falling alternately. Leuret attributes the error of personality in the deranged (of which we have seen so remarkable an instance in the St. Yon Asylum, in a man named Lambert, who believed that he died at Austerlitz) to that double action, in virtue of which all the reasonings, objections, and remarks which they use in their arguments, and their dreams, lead them to think that it is another individual who thus disputes; and this obliges them to say: "They make me act; they make me speak; they drive me."

There are some hallucinated persons who converse successively with three, four, and as many as a dozen or fifteen persons, each of whose voices they profess to distinguish. Occasionally, the number of voices diminishes or augments. In the preceding examples, the deranged heard the voices but did not reply to them; the contrary might happen; in which case, actual conversations would take place; asides, with invisible characters. Under these circumstances, the persons affected often speak in two different voices.

Hallucinations are seldom under the control of the will; they are manifested without consciousness on the part of the individual. They surprise him by day and by night, and follow him everywhere. We speak chiefly of morbid hallucinations. In some cases, however, they can be conjured up at will. This fact, admitted by Mons. Baillarger, is a powerful argument against his theory of the weakening of attention. Abercrombie's patient could instantly evoke the figures he desired. So also did the celebrated Niebuhr. In the former example, the hallucinations, once produced, remained a considerable time. Many estimable men, subject to this state of the brain, have remarked that it is very difficult to reproduce, by a powerful concentration of thought, the object of the hallucination, although it appeared but a few moments previously, of itself, and without the slightest effort.