distended bladder, to the enlargement of
pregnancy, to the swelling produced by an abscess, to the overgrowth of
tissue (hyperplasia) associated with injury and consequent inflammation,
and to numerous other phases of tissue enlargement directly connected with
recognized disease processes. For this reason it is becoming more common
for scientists to apply the word "neoplasm" to the new growths described in
this chapter. Because of the still popular use of the word "tumor," it is
retained in this chapter for the designation of those new growths to which
the sevenfold characterization of our descriptive definition applies.

DISEASES OF THE SKIN.

By M. R. TRUMBOWER, D. V. S.

[Revised by John R. Mohler, V. M. D.]

GENERAL DISCUSSION.

The skin consists of two parts--a superficial layer, the epidermis, or
cuticle, and the deep, or true, skin, the dermis, cutis vera, or corium.

The epidermis, cuticle, or scarf skin, is an epithelial structure, forming
a protective covering to the corium. It varies in thickness, is quite
insensible and nonvascular, and consists of a sheet of cells.

The epidermis is divided into a firm and transparent superficial and a
deep, soft layer. The latter is the rete mucosum, whose cells contain the
pigment which gives color to the skin. The deep surface of the epidermis is
accurately molded on the papillary layer of the true skin, and, when
removed by maceration, presents depressions which correspond to the
elevations on the dermis. From the cuticle tubular prolongations pass into
the sebaceous and sudorific glands; thus the entire surface of the body is
inclosed by the cuticle.

The dermis, or true skin, is vascular and highly sensitive, containing the
tactile ends of the nerves of touch. It is covered by epidermis and
attached to the underlying parts by a layer of areolar tissue, which
usually contains fat. The cutis consists of a fibro-areolar tissue and
vessels of supply. It is divided into two layers, the deep, or true, corium
and the upper, or papillary. The corium consists of strong interlacing
fibrous bands, chiefly white; its meshes are larger and more open toward
the attached surface, giving lodgment to the sweat glands and fat. The
papillary, or superficial, layer is formed of a series of small conical
eminences or papillae, which are highly sensitive, and consists of a
homogenous, transparent tissue. The blood vessels form dense capillary
plexuses in the corium, termina