ited by the pain in consequence of
the increased contractions of those moving fibres.

And in insane people in some cases the force of their muscular actions will
be in proportion to the quantity of sensorial power, which they possess,
and the quantity of the stimulus of desire or aversion, which excites their
volition into action. At the same time in other cases the stimulus of pain
or pleasure, and the stimulus of external bodies, may excite into action
the sensorial powers of sensation and irritation, and thus add greater
force to their muscular actions.

2. The application of the stimulus, whether that stimulus be some quality
of external bodies, or pleasure or pain, or desire or aversion, or a link
of association, excites the correspondent sensorial power into action, and
this causes the contraction of the fibre. On the contraction of the fibre a
part of the spirit of animation becomes expended, and the fibre ceases to
contract, though the stimulus continues to be applied; till in a certain
time the fibre having received a supply of sensorial power is ready to
contract again, if the stimulus continues to be applied. If the stimulus on
the contrary be withdrawn, the same quantity of quiescent sensorial power
becomes resident in the fibre as before its contraction; as appears from
the readiness for action of the large locomotive muscles of the body in a
short time after common exertion.

But in those muscular fibres, which are subject to constant stimulus, as
the arteries, glands, and capillary vessels, another phenomenon occurs, if
their accustomed stimulus be withdrawn; which is, that the sensorial power
becomes accumulated in the contractile fibres, owing to the want of its
being perpetually expended, or carried away, by their usual unremitted
contractions. And on this account those muscular fibres become afterwards
excitable into their natural actions by a much weaker stimulus; or into
unnatural violence of action by their accustomed stimulus, as is seen in
the hot fits of intermittent fevers, which are in consequence of the
previous cold ones. Thus the minute vessels of the skin are constantly
stimulated by the fluid matter of heat; if the quantity of this stimulus of
heat be a while diminished, as in covering the hands with snow, the vessels
cease to act, as appears from the paleness of the skin; if this cold
application of snow be continued but a short time, the sensorial power,
which had habitually been supp