t increase of the
stimulus of heat and momentum, produce more violent exertions than those
above described; great pain arises in some part of the moving system, as in
the membranes of the brain, pleura, or joints; and new motions of the
vessels are produced in consequence of this pain, which are called
inflammation; or delirium or stupor arises; as explained in Sect. XXI. and
XXXIII.: for the immediate effect is the same, whether the great energy of
the moving organs arises from an increase of stimulus or an increase of
irritability; though in the former case the waste of sensorial power leads
to debility, and in the latter to health.

_Recapitulation._

X. Those muscles, which are less frequently exerted, and whose actions are
interrupted by sleep, acquire less accumulation of sensorial power during
their quiescent state, as the muscles of locomotion. In these muscles after
great exertion, that is, after great exhaustion of sensorial power, the
pain of fatigue ensues; and during rest there is a renovation of the
natural quantity of sensorial power; but where the rest, or quiescence of
the muscle, is long continued, a quantity of sensorial power becomes
accumulated beyond what is necessary; as appears by the uneasiness
occasioned by want of exercise; and which in young animals is one cause
exciting them into action, as is seen in the play of puppies and kittens.

But when those muscles, which are habituated to perpetual actions, as those
of the stomach by the stimulus of food, those of the vessels of the skin by
the stimulus of heat, and those which constitute the arteries and glands by
the stimulus of the blood, become for a time quiescent, from the want of
their appropriated stimuli, or by their associations with other quiescent
parts of the system; a greater accumulation of sensorial power is acquired
during their quiescence, and a greater or quicker exhaustion of it is
produced during their increased action.

This accumulation of sensorial power from deficient action, if it happens
to the stomach from want of food, occasions the pain of hunger; if it
happens to the vessels of the skin from want of heat, it occasions the pain
of cold; and if to the arterial system from the want of its adapted
stimuli, many disagreeable sensations are occasioned, such as are
experienced in the cold fits of intermittent fevers, and are as various, as
there are glands or membranes in the system, and are generally termed
universal une