medicines had no effect on him. He was gently awakened every half hour for
one night, but without good effect, as he soon slept again, and the fit
returned at about the same periods of time, for the accumulated sensorial
power, which occasioned the increased sensibility to pain, was not thus
exhausted. This case evinces, that the sensibility of the system to
internal excitation increases, as our sleep is prolonged; till the pain
thus occasioned produces voluntary exertion; which, when it is in its usual
degree, only awakens us; but when it is more violent, it occasions
convulsions.

The cramp in the calf of the leg is another kind of convulsion, which
generally commences in sleep, occasioned by the continual increase of
irritability from internal stimuli, or of sensibility, during that state of
our existence. The cramp is a violent exertion to relieve pain, generally
either of the skin from cold, or of the bowels, as in some diarrhoeas, or
from the muscles having been previously overstretched, as in walking up or
down steep hills. But in these convulsions of the muscles, which form the
calf of the leg, the contraction is so violent as to occasion another pain
in consequence of their own too violent contraction; as soon as the
original pain, which caused the contraction, is removed. And hence the
cramp, or spasm, of these muscles is continued without intermission by this
new pain, unlike the alternate convulsions and remissions in epileptic
fits. The reason, that the contraction of these muscles of the calf of the
leg is more violent during their convulsion than that of others, depends on
the weakness of their antagonist muscles; for after these have been
contracted in their usual action, as at every step in walking, they are
again extended, not, as most other muscles are, by their antagonists, but
by the weight of the whole body on the balls of the toes; and that weight
applied to great mechanical advantage on the heel, that is, on the other
end of the bone of the foot, which thus acts as a lever.