these bodies and the medulla of the nerve.

As the nerves of the senses have each their appropriated objects, which
stimulate them into activity; so the muscular fibres, which are the
terminations of other sets of nerves, have their peculiar objects, which
excite them into action; the longitudinal muscles are stimulated into
contraction by extension, whence the stretching or pandiculation after a
long continued posture, during which they have been kept in a state of
extension; and the hollow muscles are excited into action by distention, as
those of the rectum and bladder are induced to protrude their contents from
their sense of the distention rather than of the acrimony of those
contents.

There are other objects adapted to stimulate the nerves, which terminate in
variety of membranes, and those especially which form the terminations of
canals; thus the preparations of mercury particularly affect the salivary
glands, ipecacuanha the stomach, aloe the sphincter of the anus,
cantharides that of the bladder, and lastly every gland of the body appears
to be indued with a kind of taste, by which it selects or forms each its
peculiar fluid from the blood; and by which it is irritated into activity.

Many of these external properties of bodies, which stimulate our organs of
sense, do not seem to effect this by a single impulse, but by repeated
impulses; as the nerve of the ear is probably not excitable by a single
vibration of air, nor the optic nerve by a single particle of light; which
circumstance produces some analogy between those two senses, at the same
time the solidity of bodies is perceived by a single application of a solid
body to the nerves of touch, and that even through the cuticle; and we are
probably possessed of a peculiar sense to distinguish the nice degrees of
heat and cold.