kin by small tubes, which traverse
the cuticle. In some parts, these glands are wanting; in others, where
their office is most needful, they are abundant, as on the face and
nose, the head, the ears, &c. In some parts, these tubes are spiral;
in others, straight. These glands offer every shade of complexity,
from the simple, straight tube, to a tube divided into numberless
ramifications, and constituting a little rounded tree-like mass, about
the size of a millet seed.

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Of what are they a part? 630. Describe the oil-glands. With what do
they connect? Do they exist in every part of the body? Of what form
are their tubes?

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631. In a few situations, these small glands are worthy of particular
notice, as in the eyelids, where they possess great elegance of
distribution and form, and open by minute pores along the lids; in the
ear-passages, where they produce that amber-colored substance, known
as the _ce-ru'men_, (wax of the ears,) and in the scalp, where they
resemble small clusters of grapes, and open in pairs into the sheath
of the hair, supplying it with a pomatum of Nature's own preparing.
The oil-tubes are sometimes called the _se-ba'ceous fol'li-cles_.

[Illustration: 4. A small hair from the scalp, with its oil-glands. The
glands (A) form a cluster around the shaft of the hair-tube, (C.) These
ducts open into the sheath of the hair, (B.) All the figures, from 1 to
4, are magnified thirty-eight diameters.]

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631. What is said of these tubes in the eyelids? In the ear? In the
scalp? What are these glands sometimes called?

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_Observation._ Among the inhabitants of cities, and especially in
persons who have a torpid state of the skin, the contents of the
oil-tubes become too dense and dry to escape in the usual manner. Thus
it collects, distends the tube, and remains until removed by art. When
this impacted matter reaches the surface, dust and smoke mix with it,
then it is recognized by small, round, dark spots. These are seen on
the forehead, nose, and other parts of the face. When this matter is
pressed out, the tube gives it a cylindrical form. The parts around
the distended tubes sometimes inflame. This constitutes the disease
called, _"ac'ne punc-ta'ta."_

632. The PERSPIRATORY APPARATUS consists of minute cylindrical tubes,
which pass inward through the cuticle, and terminate in the deeper
me