e case with
the eye, and ear.

The organ of touch is seated chiefly in the skin, but different parts
of this covering possess different degrees of sensibility. The skin
consists of three parts. 1. The cutis vera, or true skin, which
covers the greatest part of the surface of the body. When the skin is
examined by a microscope, we find it composed of an infinite number
of papillae, or small eminencies, which seem to be the extremities of
nerves, each of which is accompanied by an artery and a vein, so that
when the vessels of the skin are injected, the whole appears red. 2.
Immediately over the true skin, and filling up its various
inequalities, lies a mucous reticulated substance, which has been
called by Malpighi, who first described it, rete mucosum. The real
skin is white in the inhabitants of every climate; but the rete
mucosum is of various colours, being white in Europeans, olive in
Asiatics, black in Africans, and copper coloured in Americans. This
variety depends chiefly on the degree of light and heat; for, if we
were to take a globe, and paint a portion of it with the colour of
the inhabitants of corresponding latitudes, we should have an uniform
gradation of shade, deepening from the pole to the equator.

The diversity of colour depends upon the bleaching power of the
oxygen, which, in temperate climates, combines more completely with
the carbonaceous matter deposited in the rete mucosum; while, in
hotter climates, the oxygen is kept in a gaseous state by the heat
and light, and has less tendency to unite with the carbonaceous
matter. In proof of this, the skins of Africans may be rendered white
by exposure to the oxygneated muriatic acid.

Over the rete mucosum is spread a fine transparent membrane, called
the cuticle, or scarf skin, which defends the organ of feeling from
the action of the air, and other things which would irritate it too
powerfully. In some parts of the body this membrane is very thick, as
in the soles of the feet, and palms of the hands; and this thickness
is much increased by use and pressure.

In general, the thinner the cuticle is, the more acute is the sense
of touch. This sense is very acute and delicate about the ends of the
fingers, where we have the most need of it; but in the lips, mouth,
and tongue, it is still more delicate; a galvanic or electrical shock
being felt by the tongue, when it is impossible for us to perceive it
by the fingers.

This sense, like the others, b