heat does not render the body more liable to be
affected by food, but the reverse. Both these are stimulants, and
exhaust the excitability. But after heat has been applied, if it be
followed by cold, a great degree of languor or weakness will take
place; because we have here a direct debility, added to indirect
debility. In the same way, grief succeeding joy, or despair
succeeding hope, produce a greater degree of dejection, both of mind
and body, than if they had not been preceded by these stimulant
passions; because here, direct debility is added to indirect. The
excitability is first exhausted, and then the stimulus is withdrawn.

We see then, that the passions of the mind act as stimulants to the
body, that, when in a proper degree, they tend to preserve it in
health; but when their action is either too powerful, or too small,
they produce the same effects as the other powers. We should
therefore naturally expect, that when there is a deficient action of
this kind of mental stimulus, or when the mind is under the influence
of the depressing passions, a predisposition to diseases of direct
debility would take place, and even these diseases be produced.
Accordingly we find a numerous class of nervous complaints
originating from these causes. Indeed, the undue action of the mental
stimulants, produces more quick alterations in the state of the
excitement, than that of the other exciting powers. Violent grief, or
vexation, will immediately suspend the powers of the stomach. If we
suppose a person in the best health, and highest good humour, sitting
down to dinner with his friends, if he suddenly receives any
afflicting news, his appetite is instantly gone, he cannot swallow a
morsel. If the same thing happens after he has made a hearty dinner,
the action of the stomach is suddenly suspended, and the whole
process of digestion stopped, and what he has eaten, lies a most
oppressive load. But this is not all: the whole circulation of the
blood becomes disturbed; the contraction and dilatation of the heart
become irregular; it flutters, and palpitates; hence all the
secretions become irregular, some of the glands acting too
powerfully, others not at all; hence the increased action of the
kidneys, and hence a burst of tears; hysterical affections, epilepsy,
and syncope, frequently succeed, in which every muscle of the body
becomes convulsed. Indeed, many terrible diseases originate from this
source, which were formerly asc