When their
accustomed stimulus is for a while intermitted, as when snow is applied to
the skin of the hands, an accumulation of sensorial power is produced; and
then a degree of stimulus, as of heat, somewhat greater than that at
present applied, though much less than the natural quantity, excites the
vessels of the skin into violent action. We must observe, that a deficiency
of stimulus in those fibres, which are not subject to perpetual stimulus,
as the locomotive muscles, is not succeeded by accumulation of sensorial
power; these therefore are more liable to become permanently inactive after
a diminution of stimulus; as in strokes of the palsy, this may be called
inactivity from defect of stimulus.

2. A second source of animal inactivity exists, when the sensorial power in
any part of the system has been previously exhausted by violent stimuli; as
the eyes after long exposure to great light; or the stomach, to repeated
spirituous potation; this may be termed inactivity from exhaustion of
sensorial power. See Sect. XII. 2. 1.

3. But there is a third source of inactivity owing to the deficient
production of sensorial power in the brain; and hence stimuli stronger than
natural are required to produce the accustomed motions of the arterial
system; in this case there is no accumulation of sensorial power produced;
as in the inactivity owing to defect of stimulus; nor any previous
exhaustion of it, as in the inactivity owing to excess of stimulus.

This third kind of inactivity causes many of the diseases of this genus;
which are therefore in general to be remedied by such medicines as promote
a greater production of sensorial power in the brain; as the incitantia,
consisting of wine, beer, and opium, in small repeated quantities; and
secondly of such as simply stimulate the arterial and glandular system into
their natural actions; as small repeated blisters, spices, and essential
oils. And lastly the sorbentia, which contribute to supply the more
permanent strength of the system, by promoting the absorption of
nourishment from the stomach, and intestines; and of the superfluous fluid,
which attends the secretions.

SPECIES.

1. _Febris inirritativa._ Inirritative fever. This is the typhus mitior, or
nervous fever of some writers; it is attended with weak pulse without
inflammation, or symptoms of putridity, as they have been called. When the
production of sensorial power in the brain is less than usual, the pulse
b