bone of thousands of years ago were similar in their manifestations to those same diseases of bone of today. From the writings of the early Egyptian, Greek, and Roman physicians we identify diseases by their symptoms, and recognize that the symptoms of these diseases have not changed throughout the ages. Therefore, with the knowledge of the signs and symptoms of various diseases which we have today, we can safely assert that if an ancient complained of the same group of signs and symptoms (which is now termed a "disease complex"), he was suffering from the same disease which we can identify in modern man.
What applies to physical disease is just as applicable to mental disease. In speaking of mental disease, it is important for the layman to keep in mind a few fundamental principles held by the physician. The physician in speaking of mental disease means a more or less permanent departure from the normal or usual way of thinking, acting, or feeling. In the examination of a patient with mental disease the physician looks for delusions, illusions, and hallucinations.
A delusion is a false belief, concerning which the individual who holds it is unable to admit evidence such as would be admitted by ordinary individuals.
An illusion is a deception of the senses, a misinterpretation of sensory impressions; the normal person can be convinced of this deception. The mirage, for example, is an optical illusion which has a starting point in an external stimulus.
A hallucination is a deception of any of the five senses, in which there is no starting point but it is fabricated in a disordered mind. Illustrations of hallucinations are the hearing of voices when none are present, smelling of odors, the seeing of visions in a vacuum.
With the elementary understanding of fundamental
