the pain when a portion of the outer skin has been
removed.

The skin, being richly supplied with nerves, is an important organ of
sensibility and touch. In some parts it is closely attached to
the structures beneath, while in others it is less firmly adherent and
rests upon a variable amount of fatty tissue. It thus assists in relieving
the abrupt projections and depressions of the general surface, and in
giving roundness and symmetry to the entire body. The thickness of the
skin varies in different parts of the body. Where exposed to pressure and
friction, as on the soles of the feet and in the palms of the hands, it is
much thickened.

The true skin is 1/12 to 1/8 of an inch in thickness, but in certain
parts, as in the lips and ear passages, it is often not more than 1/100 of
an inch thick. At the orifices of the body, as at the mouth, ears, and
nose, the skin gradually passes into mucous membrane, the structure of the
two being practically identical. As the skin is an outside covering, so is
the mucous membrane a more delicate inside lining for all cavities into
which the apertures open, as the alimentary canal and the lungs.

[Illustration: Fig. 97.--A Layer of the Cuticle from the Palm of the Hand.
(Detached by maceration.)]

The skin ranks as an important organ of excretion, its product being
sweat, excreted by the sweat glands. The amount of this excretion
evaporated from the general surface is very considerable, and is modified
as becomes necessary from the varied conditions of the temperature. The
skin also plays an important part in regulating the bodily
temperature(sec. 241).

234. The Cutis Vera, or True Skin. The skin is remarkably complex in
its structure, and is divided into two distinct layers, which may be
readily separated: the deeper layer,--the true skin, dermis, or
corium; and the superficial layer, or outer skin,--the epidermis,
cuticle, or scarf skin.

The true skin consists of elastic and white fibrous tissue, the
bundles of which interlace in every direction. Throughout this feltwork
structure which gradually passes into areolar tissue are numerous muscular
fibers, as about the hair-follicles and the oil glands. When these tiny
muscles contract from cold or by mental emotion, the follicles project
upon the surface, producing what is called "goose flesh."

The true skin is richly supplied with blood-vessels and nerves, as when
cut it bleeds freely, and is very sensitive. The surface of