the addition of inflammation.

4. In these putrid or malignant fevers a deficiency of irritability
accompanies the increase of sensibility; and by this waste of sensorial
power by the excess of sensation, which was already too small, arises the
delirium and stupor which so perpetually attend these inflammatory fevers
with arterial debility. In these cases the voluntary power first ceases to
act from deficiency of sensorial spirit; and the stimuli from external
bodies have no effect on the exhausted sensorial power, and a delirium like
a dream is the consequence. At length the internal stimuli cease to excite
sufficient irritation, and the secretions are either not produced at all,
or too parsimonious in quantity. Amongst these the secretion of the brain,
or production of the sensorial power, becomes deficient, till at last all
sensorial power ceases, except what is just necessary to perform the vital
motions, and a stupor succeeds; which is thus owing to the same cause as
the preceding delirium exerted in a greater degree.

This kind of delirium is owing to a suspension of volition, and to the
disobedience of the senses to external stimuli, and is always occasioned by
great debility, or paucity of sensorial power; it is therefore a bad sign
at the end of inflammatory fevers, which had previous arterial strength, as
rheumatism, or pleurisy, as it shews the presence of great exhaustion of
sensorial power in a system, which having lately been exposed to great
excitement, is not so liable to be stimulated into its healthy action,
either by additional stimulus of food and medicines, or by the accumulation
of sensorial power during its present torpor. In inflammatory fevers with
debility, as those termed putrid fevers, delirium is sometimes, as well as
stupor, rather a favourable sign; as less sensorial power is wasted during
its continuance (see Class II. 1. 6. 8.), and the constitution not having
been previously exposed to excess of stimulation, is more liable to be
excited after previous quiescence.

When the sum of general pleasurable sensation becomes too great, another
kind of delirium supervenes, and the ideas thus excited are mistaken for
the irritations of external objects: such a delirium is produced for a time
by intoxicating drugs, as fermented liquors, or opium: a permanent delirium
of this kind is sometimes induced by the pleasures of inordinate vanity, or
by the enthusiastic hopes of heaven. In these cases the