an insanity of short
duration; for insanities generally, though not always, arise from pains of
the organs of sense; but convulsions generally, though not always, from
pains of the membranes or glands. And it has been previously explained,
that though the membrane and glands, as the stomach and skin, receive great
pain from want of stimulus; yet that the organs of sense, as the eye and
ear, receive no pain from defect of stimulus.

Hence it follows, that the constitutions most liable to convulsion, are
those which most readily become torpid in some part of the system, that is,
which possess less irritability; and that those most liable to insanity,
are such as have excess of sensibility; and lastly, that these two
circumstances generally exist in the same constitution; as explained in
Sect. XXXI. 2. on Temperaments. These observations explain why epilepsy and
insanity frequently succeed or reciprocate with each other, and why
inirritable habits, as scrophulous ones, are liable to insanity, of which I
have known some instances.

In many cases however there is no appearance of the disposition to epilepsy
or insanity of the parent being transmitted to the progeny. First, where
the insanity has arisen from some violent disappointment, and not from
intemperance in the use of spirituous liquors. Secondly, where the parent
has acquired the insanity or epilepsy by habits of intoxication after the
procreation of his children. Which habits I suppose to be the general cause
of the disposition to insanity in this country. See Class III. 1. 1. 7.

As the disposition to gout, dropsy, epilepsy, and insanity, appears to be
produced by the intemperate use of spirituous potation, and is in all of
them hereditary; it seems probable, that this disposition gradually
increases from generation to generation, in those families which continue
for many generations to be intemperate in this respect; till at length
these diseases are produced; that is, the irritability of the system
gradually is decreased by this powerful stimulus, and the sensibility at
the same time increased, as explained in Sect. XXXI. 1. and 2. This
disposition is communicated to the progeny, and becomes still increased, if
the same stimulus be continued, and so on by a third and fourth generation;
which accounts for the appearance of epilepsy in the children of some
families, where it was never known before to have existed, and could not be
ascribed to their own intemperanc