is caused by a sudden, violent expulsion of air from the chest
following the drawing in of a deep breath. A loose cough is to be
encouraged, as by its means mucus and other discharge is expelled from
the air passages.

A dry cough is seen in the early stages of various respiratory
diseases, as bronchitis, pneumonia, pleurisy, consumption, whooping
cough, and with irritation from enlarged tonsils and adenoids (see p.
61) occurring in children.

Irritation produced by inhaling dust, or any irritation existing in
the nose, ear, or throat may lead to this variety of cough. The dry
cough accomplishes no good, and if continuous and excessive may do
harm, and demands medicinal relief.

=Bronchitis.=--Cough following or accompanying cold in the head and
sore throat generally means bronchitis.

The larynx or lower part of the throat ends just below the "Adam's
apple" in the windpipe. The windpipe is about four and a half inches
long and three-quarters to an inch in diameter, and terminates by
dividing into the two bronchial tubes in the upper part of the chest.
Each bronchial tube divides and subdivides in turn like the branches
of a tree, the branches growing more numerous and smaller and smaller
until they finally end in the microscopic air sacs or air cells of the
lungs. The bronchial tubes convey air to the air cells, and in the
latter the oxygen is absorbed into the blood, and carbonic acid is
given up. Bronchitis is an inflammation of the mucous membrane lining
these tubes. In cough of an ordinary cold only the mucous membrane of
the windpipe and, perhaps, of the larger tubes is inflamed. This is a
very mild disorder compared to inflammation of the smaller and more
numerous tubes.

In bronchitis, besides the ordinary symptoms of a severe cold in the
head, as sneezing, running of mucus from the nose, sore throat and
some hoarseness perhaps, and languor and soreness in the muscles,
there is at first a feeling of tightness, pressure, and rawness in the
region of the breastbone, with a harsh, dry cough. The coughing causes
a strain of the diaphragm (the muscle which forms the floor of the
chest), so that there are often pain and soreness along the lower
borders of the chest where the diaphragm is attached to the inside of
the ribs. After a few days the cough becomes looser, greatly to the
patient's comfort, and a mixture of mucus and pus is expectorated. In
a healthy adult such a cough is usually not in itself a serious