tter.

Impetigo is marked by the formation of yellow pus, which raises the
cuticle into pustules. There is a slight swelling, redness, and the pus
gradually dries up, forming an amber-colored crust, a representation of
which is given in Colored Plate I, Fig. 5. It soon falls, leaving the
skin slightly inflammed, but with no scar. The pustules are sometimes
surrounded by a cluster of smaller ones.

The varieties of impetigo are designated according to the distribution
of the pustules. _Impetigo figurata_, is characterized by the appearance
of large clusters upon an inflamed and swollen surface, generally upon
the face, but sometimes upon the scalp. This form is represented in
Colored Plate I, Fig. 4. In _impetigo sparsa_ the pustules are scattered
over the whole body.

CAUSES. The predisposing cause of impetigo is nutritive debility, and
the exciting causes are irritation, impure air, and errors of diet.

GUTTA ROSACEA is a _progressive_ disease, and its successive stages of
development mark the several varieties, such as _gutta rosacea,
erythematosa, papulosa, tuberculosa, pustulosa_, according as they are
characterized by redness, pimples, tubercles, or pustules. This
affection is attended with heat, itching, and throbbing. The pustules
contain serous lymph, which exudes if the cuticle be broken, and forms a
crust at the summit of the pustule.

This eruption often appears on the face of persons addicted to
intemperate habits, and has thus received the name of "_rum blossom_."

CAUSE. It is essentially a chronic affection, and depends upon
constitutional causes.

SCABIES. (_Itch_.) This disease is characterized by a profuse scaliness
of the skin, by an eruption of pimples, vesicles, and, in rare
instances, of pustules. Its prominent feature is an intense itching, so
aggravating that, in many instances, the skin is torn by the nails.
Unlike other diseases of the skin, it is not due to inflammation, but is
caused by animalculae, or little parasites, termed by naturalists the
_acarus scabiei_. This minute animal burrows in the skin, irritating it,
and thus producing the scaliness and itching. The vesicles are
comparatively few in number, and contain a transparent fluid. The
pustules are only present in the severest forms or when the skin is very
thin and tender. It is then termed _pustular itch_.

The parts usually affected are the hands, flexures of the joints, and
the genital organs. Cases are recorded, in which