r medium, as
when the hands are immersed in iced water for a minute, these capillary
vessels and their glands become torpid or quiescent, owing to the eduction
of the stimulus of heat. The skin then becomes pale, because no blood
passes through the external capillaries; and appears shrunk, because their
sides are collapsed from inactivity, not contracted by spasm; the roots of
the hair are left prominent from the seceding or subsiding of the skin
around them; and the pain of coldness is produced.

In this situation, if the usual degree of warmth be applied, these vessels
regain their activity; and having now become more irritable from an
accumulation of the sensorial power of irritation during their quiescence,
a greater exertion of them follows, with an increased glow of the skin, and
another kind of pain, which is called the hot-ach; but no fever, properly
so called, is yet produced; as this effect is not universal, nor permanent,
nor recurrent.

2. If a greater part of the cutaneous capillaries with their mucous and
perspirative glands be exposed for a longer time to cold, the torpor or
quiescence becomes extended by direct sympathy to the heart and arteries;
which is known by the weakness, and consequent frequency of the pulse in
cold fits of fever.

This requires to be further explained. The movements of the heart and
arteries, and the whole of the circulatory vessels, are in general excited
into action by the two sensorial powers of irritation, and of association.
The former is excited by stimulus, the latter by the previous actions of a
part of the vital circle of motions. In the above situation the capillaries
act weakly from defect of irritation, which is caused by deficient stimulus
of heat; but the heart and arteries act weakly from defect of association,
which is owing to the weak action of the capillaries; which does not now
excite the sensorial power of association into action with sufficient
energy.

After a time, either by the application of warmth, or by the increase of
their irritability owing to the accumulation of the sensorial power of
irritation during their previous quiescence, the capillary vessels and
glands act with greater energy than natural; whence the red colour and heat
of the skin. The heart and arteries acquire a greater strength of
pulsation, and continue the frequency of it, owing to the accumulation of
the sensorial power of association during their previous torpor, and their
cons