The following definition are taken from Dr. Ireland's work entitled, "The Blot upon the Brain."

He says, "Illusions are erroneous interpreta-tions of real sensations, that is, sensationsorigin-ating from changes in the outer world acting on some part of the nervous system. Thus, a man mistakes a rock for a tower, or the play of the moonlight through the forest leaves for running water, or a sheet hung up for a ghost. In these instances the mind has been too rapid in its forecast, either by following the line of habit acquired in cases outwardly similar, or by yielding to the suggestions of hope and fear, or by following the fallacies of a disordered mind.

"A hallucination is a perception of a sensation arising from changes within the organism without any corresponding change in the outer world. It is a perception that has no object. Hallucinations have been divided into 'elementary' and 'elaborated.' Thus, a flash of light, or a sound in the ear, is a simple hallucination; but if a man believes he sees a figure or hears a voice which has no outward existence, it is an elaborated hallucination. This subjective irritation of the optic or auditory nerve appears to him to bo the same as the image of some figure or sound already existing in his mind."

This part of my subject will be a very difficult one for the lay reader to grasp, and hallucinations have played so important a part in the history of the world that it seems to me that the general public should have a better understanding of them. They do not occur in the violently insane alone. Probably very few sane people go through life without some time or another experiencing either hallucinations or illusions, or both. They have been mistaken for supernatural appearances. Voices originating in the brains of men have commanded them to do hideous things, and whole systems of religion have arisen as products of a diseased brain, caused possibly by an undigested beef-steak. Wills have been made, homes broken up, and lives wrecked, because these fancies were mistaken for Divine utterances. Voices, children of a perverted imagination, tell us queer things by night. Our dreams make up a large integral part of our consciousness.

Before proceeding let us consider what we mean by certain words which will be used in this chapter.

Imagination is, 1. The image-making power of the mind, the power to create or reproduce ideally an object of sense previously perceived; the power to call up mental images. 2. The representative power; the power to reconstruct or recombine the materials furnished by direct apprehension; the fancy. 3. The power to re-combine the materials furnished by direct memory for the accomplishment of a purpose. 4. A mental image formed by an action of the imagination as a faculty.

From the foregoing definitions it will be clear that hallucinations arising from the imagination are very complex indeed. If we associate with the word "imagination" the word 'voluntary" our conception will beat once changed. Who cannot call up at will the face of some loved one, who has either gone to death's dateless night, or who is journeying in some far-off land? Memory, the twin sister of imagination, when acting in concert with her, can produce anew upon the mind of an old man the glorious imagery of bis childhood, and he lives again the joys of his youth. Hallucinations are not always, in fact are very seldom, the result of the voluntary exercise of imagination.

An eminent physician became insane and suffered many and varied hallucinations.

After being restored to health he says: "The only influence which the will had over the hallucinations during my illness was that it could place me in a favorable position for receiving them." He says it never succeeded either in intentionally calling before him hallucinations, or in changing a recollection or a product of the fancy into a hallucination, or in recalling by will one which had recently appeared to him. Hence, apparently, the view of Lelut, that hallucinations are simply thoughts, is erroneous.

Hallucinations are very common among those who are partially insane. They occur as a result of fever and frequently accompany delirium. They result from an impoverished condition of the blood, especially if it is due to starvation, indigestion, and the use of drugs like belladonna, hyoscyamus, stramonium, opium, chloral, cannabis indica, and many more that might be mentioned.

Probable Physical Causation of Hallucinations. Dr. Bouchard of Paris has carried on experiments for a number of years which prove that there are many poisonous products, formed during the process of digestion, which act upon the brain in a similar way to many of the drugs mentioned. Sow, if digestion be arrested at a certain stage, these products pass into the blood, act through it upon the cells of the brain, and weird fancies, strange voices, and queer forms haunt the habitations of the mind. Some of these so-called alkaloids have been isolated and their physiological action studied. Also, recently, a substance has been found in the secretions taken from patients suffering from melancholia, which, when injected into animals, gives rise to phenomena which are similar to, if not identical with, those observed in this form of insanity among men.

The whole theory of auto-intoxication promises to throw much light upon both the cause and the treatment of many obscure mental diseases. It is well known that there are substances formed as a result of putrefactive changes in dead bodies which are highly poisonous. Some of them belong to the so-called nerve-poisons. Some are irritants of the mucous membrane. It is now equally well established that many substances are thrown off by the secretions from the live body, which will act in the same way as substances formed after death.

Prof. Bouchard has proved that during the waking hours a person secretes a substance which is carried off by the urine, and when this substance is injected into the lower animals, it causes them to sleep, and, strange as it is, this eminent professor has found, by experimentation, in the urines passed off by sleeping persona, a substance which acts as a cerebral excitant, producing, when injected into the lower animals, delirium, insanity and convulsions. These substances be succeeded, by the use of alcohol and other chemical means, in extracting from the urine, purified many of them and affixed names to them.