cells, vessels, nerves, glands,
gland ducts, hairs, and in the deeper layers fat.

The superficial layer of the dermis is formed into a series of minute,
conical elevations, or papillae, projecting into the deep portion of the
cuticle, from which they are separated by a very fine transparent
membrane. This papillary layer is very richly supplied with capillary
blood vessels and nerves, and is at once the seat of acute sensation and
the point from which the nutrient liquid is supplied to the cells of the
cuticle above. It is also at this point that the active changes of
inflammation are especially concentrated; it is the immediately
superposed cell layers (mucous) that become morbidly increased in the
earlier stages of inflammation; it is on the surface of the papillary
layer that the liquid is thrown out which raises the cuticle in the form
of a blister, and it is at this point mainly that pus forms in the
ordinary pustule.

The fibrous bundles of the true skin contain plain, muscular fibers,
which are not controlled by the will, but contract under the influence
of cold and under certain nervous influences, as in some skin diseases
and in the chill of a fever, and lead to contraction, tightening, or
corrugation of the skin, contributing to produce the "hidebound" of the
horseman. Other minute, muscular filaments are extended from the surface
of the dermis to the hair follicle on the side to which the hair is
inclined, and under the same stimulating influences produce that
erection of the hair which is familiarly known as "staring coat."
Besides these, the horse's skin is furnished with an expansion of red,
voluntary muscle, firmly attached to the fibrous bundles, and by which
the animal can not only dislodge insects and other irritants, but even
shake off the harness. This fleshy envelope covers the sides of the
trunk and the lower portions of the neck and head, the parts unprotected
by the mane and tail, and serves to throw the skin of these parts into
puckers, or ridges, in certain irritating skin diseases.

The hairs are cuticular products growing from an enlarged papilla lodged
in the depth of a follicle or sac, hollowed out in the skin and
extending to its deepest layers. The hair follicle is lined by cells of
epidermis, which at the bottom are reflected on the papilla and become
the root of the hair. The hair itself is formed of the same kind of
cells firmly adherent to one another by a tough, intercellular
su