tion, it becomes epilepsy: the fits of which in some
patients generally commence during sleep. This differs from the night-mare
described in No. 3. of this Section, because in that the disagreeable
sensation is not so great as to excite the power of volition into action;
for as soon as that happens, the disease ceases.

Another circumstance, which sometimes awakes people soon after the
commencement of their sleep, is where the voluntary power is already so
great in quantity as almost to prevent them from falling asleep, and then a
little accumulation of it soon again awakens them; this happens in cases of
insanity, or where the mind has been lately much agitated by fear or anger.
There is another circumstance in which sleep is likewise of short duration,
which arises from great debility, as after great over-fatigue, and in some
fevers, where the strength of the patient is greatly diminished, as in
these cases the pulse intermits or flutters, and the respiration is
previously affected, it seems to originate from the want of some voluntary
efforts to facilitate respiration, as when we are awake. And is further
treated of in Vol. II. Class I. 2. 1. 2. on the Diseases of the Voluntary
Power. Art. Somnus interruptus.

15. We come now to those motions which depend on irritation. The motions of
the arterial and glandular systems continue in our sleep, proceeding slower
indeed, but stronger and more uniformly, than in our waking hours, when
they are incommoded by external stimuli, or by the movements of volition;
the motions of the muscles subservient to respiration continue to be
stimulated into action, and the other internal senses of hunger, thirst,
and lust, are not only occasionally excited in our sleep, but their
irritative motions are succeeded by their usual sensations, and make a part
of the farrago of our dreams. These sensations of the want of air, of
hunger, thirst, and lust, in our dreams, contribute to prove, that the
nerves of the external senses are also alive and excitable in our sleep;
but as the stimuli of external objects are either excluded from them by the
darkness and silence of the night, or their access to them is prevented by
the suspension of volition, these nerves of sense fall more readily into
their connexions with sensation and with association; because much
sensorial power, which during the day was expended in moving the external
organs of sense in consequence of irritation from external stimuli,