3. If after long quiescence from defect of stimulus the fibres, which had
previously been habituated to perpetual stimulus, are again exposed to but
their usual quantity of it; as in those who have suffered the extremes of
cold or hunger; a violent exertion of the affected organ commences, owing,
as above explained, to the great accumulation of sensorial power. This
violent exertion not only diminishes the accumulated spirit of animation,
but at the same time induces pleasure or pain into the system, which,
whether it be succeeded by inflammation or not, becomes an additional
stimulus, and acting along with the former one, produces still greater
exertions; and thus reduces the sensorial power in the contracting fibres
beneath its natural quantity.

When the spirit of animation is thus exhausted by useless exertions, the
organ becomes torpid or unexcitable into action, and a second fit of
quiescence succeeds that of abundant activity. During this second fit of
quiescence the sensorial power becomes again accumulated, and another fit
of exertion follows in train. These vicissitudes of exertion and inertion
of the arterial system constitute the paroxysms of remittent fevers; or
intermittent ones, when there is an interval of the natural action of the
arteries between the exacerbations.

In these paroxysms of fevers, which consist of the libration of the
arterial system between the extremes of exertion and quiescence, either the
fits become less and less violent from the contractile fibres becoming
coming less excitable to the stimulus by habit, that is, by becoming
accustomed to it, as explained below XII. 3. 1. or the whole sensorial
power becomes exhausted, and the arteries cease to beat, and the patient
dies in the cold part of the paroxysm. Or secondly, so much pain is
introduced into the system by the violent contractions of the fibres, that