Perversion is morbid alteration of function which may occur in emotional, intellectual, or volitional fields.
Example: The odor of a rose causing an acute sense of physical pain.
An illusion is a false interpretation of a perception.
The normal mind is quite subject to illusions, either due to a faulty sense organ, or to a preconceived state of mind which so strongly expects or presages something else than reality as to misinterpret what the senses bring.
| Examples: | The crooked stick as a snake. |
|---|---|
| A ghost created from shadow. | |
| An ordinary ringing in the ears as sleigh-bells. | |
| Milk tasting like blood. |
An hallucination is a perception without an object.
The hallucinated individual projects, as it were, the things of his mind’s creation into the outer world, and accepts them as reality. He sees snakes where there is nothing to suggest them; sees a ghost where there is no shadow; believes that the taste of blood is constantly in his mouth.
There are possible hallucinations of every sense. Nonexistent objects are seen, touched, tasted, heard, or smelled.
Hypochondriasis is a state characterized by persistent ideas of non-existent physical disabilities.
The hypochondriac has every known symptom of indigestion, or of heart disease, or is threatened with tuberculosis—all in his mind; and whatever the disorder he seizes upon, his attention hovers there, while the ideas of that particular disability persist and strengthen.