lates in drops of sweat, during long-continued
exercise or exposure to a high temperature. The office of the
perspiration is two-fold. It removes noxious matter from the system, and
diminishes animal heat, and thereby equalizes the temperature of the
body. It also renders the skin soft and pliable, thus better adapting it
to the movements of the muscles. The _Sebaceous Glands_, which are
placed in the true skin, are less abundant where the sudoriferous glands
are most numerous, and _vice versa_. Here, as elsewhere, nature acts
with systematic and intelligent design. The perspiratory glands are
distributed where they are most needed,--in the eyelids, serving as
lubricators; in the ear passages, to produce the _cerumen_, or wax,
which prevents the intrusion of small insects; and in the scalp, to
supply the hair with its natural pomatum.

[Illustration: Fig. 48.
A perspiratory gland, highly
magnified. 1, 1. The gland. 2, 2.
Excretory ducts uniting to form
a tube which tortuously perforates
the cuticle at 3, and opens
obliquely on its surface at 4.]

[Illustration: Fig. 49.
A representation of oil-tubes from the scalp
and nose.]

[Illustration: Fig. 50.
Anatomy of the skin. 5, 5. Cutis vera (true skin).
4, 4. Nervous tissue. 3, 3. Sensitive layer in which are
seen the nerves. 2, 2. The layer containing pigment
cells. 1, 1. Epidermis (cuticle).]

The _Epidermis_, or _Cuticle_, so called because it is _placed upon the
skin,_ is the outer layer of the skin. Since it is entirely destitute of
nerves and blood-vessels, it is not sensitive. Like the cutis vera, it
has two surfaces composed of layers. The internal, or _Rete Mucosum,_
which is made up chiefly of pigment cells, is adapted to the
irregularities of the cutis vera, and sends prolongations into all its
glandular follicles. The external surface, or epidermis proper, is
elastic, destitute of coloring matter, and consists of mere horny
scales. As soon as dry, they are removed in the form of scurf, and
replaced by new ones from the cutis vera. These scales may be removed by
a wet-sheet pack, or by friction. The cuticle is constantly undergoing
renewal. This layer serves to cover and protect the nervous tissue of
the true skin beneath. We may here observe that the cuticle contains the
pigment for coloring the skin. In dark races, as the negro, the cuticle
is very thick and filled with black pigment. The radiation of animal
heat is dependent upon the thickness and co