What Hallucinations Are
The insane man may also suffer from hallucinations. A hallucination is a false perception arising without external sensory experience. In a hallucination of sight, the disease in the brain causes irritation to be carried to the sight-centers of the brain, with a result that is similar to the impression carried to the same centers by the optic nerves when light is reflected into the eyes from some object. An insane man may be deluded with the belief that he sees a face against the wall where there is nothing at all. When the air is pure and sweet and no odor is discoverable, he may smell feathers burning, and thus reveal his hallucination of smell.
Delusions Common to Insanity
The insane man may have wrong ideas without logical reason for them. Thus, an insane man may declare that a beautiful actress is in love with him, when there is absolutely no foundation for such an idea. Or, he may believe that he can lift 500 pounds and run faster than a locomotive can go, while in reality he is so feeble as scarcely to be able to walk, and unable to dress himself. Such ideas are delusions. Sane people may be mistaken; they may have hallucinations, illusions and delusions; but they abandon their mistaken notions and correct their judgment at once, on being shown their errors. Sane people see the force of logical argument, and act upon it, abandoning all irrational ideas. The insane person, on the other hand, cannot see the force of logical argument; cannot realize the absurdity or impossibility of error. He clings to his own beliefs, for the evidence of his perverted senses or the deductions from his disease-irritation are very real to him. When we find this to be the fact we know he is insane.
Yet we must not confound delirium of fever with insanity. A patient suffering from typhoid fever may have a delusion that there is a pail by his bed into which he persists in throwing articles. Or he may have the hallucination that he is being called into the next room, and try to obey the supposed voice.
Certain delusions are commonly found in certain types of insanity. Depressed patients frequently manifest the delusion that they have committed a great sin, and are unfit to associate with anyone. Excited and maniacal patients often believe they are important personages—kings or queens, old historical celebrities, etc. Paranoiacs commonly have delusions of persecution and of a conspiracy among their relatives or their associates or rivals. Victims of alcoholic insanity have delusions regarding sexual matters, and generally charge with infidelity those to whom they are married. General paretics in most cases have delusions of grandeur; that is, false ideas of great strength, wealth, political power, beauty, etc.
The emotion which accompanies mental activity is generally exaggerated in all insane people except the demented. One sees extreme depression, or undue elation and exaltation, or silly glee and absurd joy. Intensity of emotion is frequent.
Crimes Impulsively Committed by the Insane
An interesting mental feature of many insane patients is the imperative conception, or imperative impulse. This is a strong urging felt by the patient to commit a certain act. He may know the act is wrong and dread the punishment which he expects will follow its commission. But so constantly and strongly is he impelled that he finally yields and commits the act. Crimes are thus perpetrated by the insane, with a full knowledge of their enormity. The fact that such impulses undoubtedly exist should modify the common test, as to an insane person's responsibility before the law. The statute in many countries regards an insane criminal as responsible for his act, if he knows the difference between right and wrong. This decision is unjust and the basis is wrong; for an impulse may be overwhelming, and the patient utterly helpless during its continuance. However, a patient who has committed a crime under stress of such an irresistible impulse should be put under permanent custodial care.