edges and introducing
sutures, usually fail. It is necessary to establish an opening into
the mouth, either by opening up the original duct or by making an
internal fistula in place of the external one.

#Salivary Calculi.#--Salivary calculi are most commonly met with _in
the submaxillary gland or its duct_. They consist of phosphate and
carbonate of lime with a small proportion of organic matter, and
result from the chemical action of bacteria on the saliva. In rare
cases a foreign body, such as a piece of straw, a fruit-seed, or a
fish-bone, forms the nucleus of the concretion. They vary in size from
a pea to a walnut, and are hard, of a whitish or grey colour, and
rough on the surface. Those that form in the gland itself are usually
irregular, while those met with in the duct are rounded or
spindle-shaped (Fig. 261).

[Illustration: FIG. 261.--Series of Salivary Calculi.]

A calculus in the duct gives rise to sharp lancinating pain, which is
aggravated when the patient takes food. The duct is seldom completely
obstructed, but the flow of saliva is usually so much impeded that the
gland becomes greatly swollen during meals. The swelling gradually
subsides between meals, or can be made to disappear by external
pressure. The calculus can usually be felt by means of a probe passed
along the duct, or by puncturing the swelling with a needle; or, with
one finger inside the mouth and another under the jaw, a hard lump can
be detected under the mucous membrane of the floor of the mouth. It
may be revealed by the X-rays. When the obstruction is complete, a
retention cyst forms in which suppuration is liable to occur, causing
marked aggravation of the symptoms. In some cases the wall of the duct
and the surrounding tissues become thickened and indurated, forming a
swelling which is liable to be mistaken for a malignant growth. The
treatment consists in making an incision through the mucous membrane
over the calculus and extracting it with a scoop or forceps.

INFECTIVE CONDITIONS.--#Parotitis.#--Inflammation of the parotid gland
may be non-suppurative or suppurative.

Of the _non-suppurative_ varieties the most common is the epidemic
form known as _mumps_. This is an acute infective condition, which
usually attacks young children, and implicates both glands, either
simultaneously or consecutively. It runs a definite course, which
lasts for from one to two weeks, and almost invariably ends in
resolution. The parotid gland