sal convulsion of the
voluntary motions, or by temporary madness.

In some of the unfortunate patients I have observed, the pain has risen to
an inexpressible degree, as above described, before the convulsions have
supervened; and which were preceded by screaming, and grinning; in others,
as in the common epilepsy, the convulsion has immediately succeeded the
commencement of the disagreeable sensations; and as a stupor frequently
succeeds the convulsions, they only seemed to remember that a pain at the
stomach preceded the fit, or some other uneasy feel; or more frequently
retained no memory at all of the immediate cause of the paroxysm. But even
in this kind of epilepsy, where the patient does not recollect any
preceding pain, the paroxysms generally are preceded by a quivering motion
of the under jaw, with a biting of the tongue; the teeth afterwards become
pressed together with vehemence, and the eyes are then convulsed, before
the commencement of the universal convulsion; which are all efforts to
relieve pain.

The reason why these convulsive motions are alternately exerted and
remitted was mentioned above, and in Sect. XII. 1. 3. when the exertions
are such as give a temporary relief to the pain, which excites them, they
cease for a time, till the pain is again perceived; and then new exertions
are produced for its relief. We see daily examples of this in the loud
reiterated laughter of some people; the pleasureable sensation, which
excites this laughter, arises for a time so high as to change its name and
become painful: the convulsive motions of the respiratory muscles relieve
the pain for a time; we are, however, unwilling to lose the pleasure, and
presently put a stop to this exertion, and immediately the pleasure recurs,
and again as instantly rises into pain. All of us have felt the pain of
immoderate laughter; children have been tickled into convulsions of the
whole body; and others have died in the act of laughing; probably from a
paralysis succeeding the long continued actions of the muscles of
respiration.

Hence we learn the reason, why children, who are so easily excited to laugh
by the tickling of other people's fingers, cannot tickle themselves into
laughter. The exertion of their hands in the endeavour to tickle themselves
prevents the necessity of any exertion of the respiratory muscles to
relieve the excess of pleasurable affection. See Sect. XVII. 3. 5.

Chrysippus is recorded to have died laug