obscure. The growths are usually congenital; but the
smooth, non-hairy moles may be acquired.

#Give the pathology of naevus pigmentosus.#

Microscopical examination shows a marked increase in the pigment in the
lowest layers of the rete mucosum, as well as more or less pigmentation
in the corium usually following the course of the bloodvessels; in the
verrucous variety the papillae are greatly hypertrophied, in addition to
the increased pigmentation. There is, as a rule, more or less
connective-tissue hypertrophy.

#What is the treatment of naevus pigmentosus?#

In many instances interference is scarcely called for, but when demanded
consists in the removal of the formation either by the knife, by
caustics, or by electrolysis. This last is, in the milder varieties at
least, perhaps the best method, as it is less likely to be followed by
disfiguring cicatrices. In naevus pilosus the removal of the hairs alone
by electrolysis is not infrequently followed by a decided diminution of
the pigmentation. In recent years both liquid air and carbon dioxide
have also been used successfully in the removal of these growths.
Pigmented naevi, which show the least tendency to growth or degenerative
change, should be radically removed, as they not infrequently lead to
carcinomatous and sarcomatous growths.

#Ichthyosis.#
(_Synonym:_ Fish-skin Disease.)

#Give a descriptive definition of ichthyosis.#

Ichthyosis is a chronic, hypertrophic disease, characterized by dryness
and scaliness of the skin, with a variable amount of papillary growth.

#At what age is ichthyosis first observed?#

It is first noticed in infancy or early childhood. In rare instances it
is congenital (ichthyosis congenita), and in such cases it is usually
severe, and of a grave type; the children are, as a rule, prematurely
born, and frequently do not survive many days or weeks.

#What extent of surface is involved?#

Usually the whole surface, but it is most marked upon the extensor
surfaces of the arms and legs, especially at the elbows and knees; the
face and scalp, in mild cases, often remain free.

#Name the two varieties of ichthyosis usually described.#

Ichthyosis simplex and ichthyosis hystrix, terms commonly employed to
designate the mild and severe forms respectively.

#Describe the clinical appearances of ichthyosis.#

The milder forms of the disease may be so slight as