ontagion diffused in the blood, or perhaps only by being
inserted beneath the cuticle, after a time, (as about a quarter of a
lunation,) excites the extreme vessels of the skin into certain motions,
which produce a similar contagious material, filling with it a thousand
pustules. So that by irritation, or by sensation in consequence of
irritation, or by association of motions, a material is formed by the
extremities of certain cutaneous vessels, exactly similar to the
stimulating material, which caused the irritation, or consequent sensation,
or association.

Many glands of the body have their motions, and in consequence their
secreted fluids, affected by pleasurable or painful ideas, since they are
in many instances influenced by sensitive associations, as well as by the
irritations of the particles of the passing blood. Thus the idea of meat,
excited in the minds of hungry dogs, by their sense of vision, or of smell,
increases the discharge of saliva, both in quantity and viscidity; as is
seen in its hanging down in threads from their mouths, as they stand round
a dinner-table. The sensations of pleasure, or of pain, of peculiar kinds,
excite in the same manner a great discharge of tears; which appear also to
be more saline at the time of their secretion, from their inflaming the
eyes and eye-lids. The paleness from fear, and the blush of shame, and of
joy, are other instances of the effects of painful, or pleasurable
sensations, on the extremities of the arterial system.

It is probable, that the pleasurable sensation excited in the stomach by
food, as well as its irritation, contributes to excite into action the
gastric glands, and to produce a greater secretion of their fluids. The
same probably occurs in the secretion of bile; that is, that the
pleasurable sensation excited in the stomach, affects this secretion by
sensitive association, as well as by irritative association.

And lastly it would seem, that all the glands in the body have their
secreted fluids affected, in quantity and quality, by the pleasurable or
painful sensations, which produce or accompany those secretions. And that
the pleasurable sensations arising from these secretions may constitute the
unnamed pleasure of exigence, which is contrary to what is meant by tedium
vitae, or ennui; and by which we sometimes feel ourselves happy, without
being able to ascribe it to any mental cause, as after an agreeable meal,
or in the beginning of intoxicati