the _nerves_;
these are the vehicles of sensation, every other part of the body being,
of itself, totally insensible.

CAROLINE.

They must then be spread through every part of the frame, for we are
every where susceptible of feeling.

EMILY.

Excepting the nails and the hair.

MRS. B.

And those are almost the only parts in which nerves cannot be
discovered. The common source of all the nerves is the brain; thence
they descend, some of them through different holes of the skull, but the
greatest part through the back bone, and extend themselves by
innumerable ramifications throughout the whole body. They spread
themselves over the muscles, penetrate the glands, wind round the
vascular system, and even pierce into the interior of the bones. It is
most probably through them that the communication is carried on between
the mind and the other parts of the body; but in what manner they are
acted on by the mind, and made to re-act on the body, is still a
profound secret. Many hypotheses have been formed on this very obscure
subject, but they are all equally improbable, and it would be useless
for us to waste our time in conjectures on an enquiry, which, in all
probability, is beyond the reach of human capacity.

CAROLINE.

But you have not mentioned those particular nerves that form the senses
of hearing, seeing, smelling, and tasting?

MRS. B.

They are considered as being of the same nature as those which are
dispersed over every part of the body, and constitute the general sense
of feeling. The different sensations which they produce arise from their
peculiar situation and connection with the several organs of taste,
smell, and hearing.

EMILY.

But these senses appear totally different from that of feeling?

MRS. B.

They are all of them sensations, but variously modified according to the
nature of the different organs in which the nerves are situated. For, as
we have formerly observed, it is by contact only that the nerves are
affected. Thus odoriferous particles must strike upon the nerves of the
nose, in order to excite the sense of smelling; in the same manner that
taste is produced by the particular substance coming in contact with the
nerves of the palate. It is thus also that the sensation of sound is
produced by the concussion of the air striking against the auditory
nerve; and sight is the effect of the light falling upon the optic
nerve. These various senses, therefore, are affected only by