(From deliro, to rave, or talk idly). It Is termed also alienatio mentis, paranoiae paraphrenesis, dementia, sometimes emolio. When the ideas excited in the mind do not correspond to the external objects, but are produced by a diseased state of the common sensory, the patient is said to be delirious. In madness, reason is destroyed; in foolishness (morosis), is defective; and in the delirium, vitiated. Delirium is commonly a symptom of fever, occasionally the effect of narcotic poisons. In general, the objects do not produce the accustomed impression, or are followed by the usual associations. It usually arises from an unequal state of activity in different parts of the brain, and differs from madness only in duration, or the presence of a disease of which it is a symptom.

Galen observes, that delirium is caused by the heat and acrimony of the fluid, but principally by yellow bile. (See his book De Sympt. Caus. lib. ii.) Many other writers think that the bile is the cause. No great danger is to be apprehended from delirium, whilst the pulse, the appetite, and respiration, arc favourable.

Delirium maniacum. See Mania.