less oblique
and is higher behind than in front. When due to a direct blow, for
example by a fist, the discoloration is limited, while it is usually
diffused over the neck when due to the passage of a wheel over the
part.

The clinical importance of these injuries depends on the complications
that may ensue; for example, extravasation of blood under the
cervical fascia may press upon the air-passage and oesophagus to such
an extent as to cause interference with breathing and swallowing; the
larynx or the trachea may be so grossly damaged that death results
immediately from suffocation, or later from gradually increasing
oedema causing obstruction of the glottis. If the mucous membrane of
the air-passage or the apex of the lung and its investing pleura is
torn, emphysema of the connective tissue may develop and spread widely
over the body. In contusions of the lower part of the neck the cords
of the brachial plexus may be injured.

#Fractures of the Hyoid, Larynx, and Trachea.#--The _hyoid bone_, on
account of its mobility and the protection it receives from the body
of the mandible, is seldom fractured, except in old people in whom the
great cornu has become ossified to the body of the bone. It is usually
broken either by a direct blow, or by transverse pressure as in
garrotting. The fracture is almost always at the junction of the great
cornu with the body, and there is marked displacement of the
fragments, which may injure the pharyngeal mucous membrane.

The _thyreoid and cricoid cartilages_ are also liable to be fractured
in run-over accidents, particularly in old people after calcification
or ossification has taken place.

The _trachea_ may be lacerated, or even completely torn from the
larynx, by the same forms of injury as produce fracture of the
laryngeal cartilages.

The _clinical features_ common to all these injuries are swelling and
discoloration; and if the mucous membrane is torn, air may escape into
the tissues and produce emphysema. There is always more or less
difficulty in breathing, which may amount to actual suffocation, and
this may come on immediately, or in the course of a few hours from
oedema of the glottis. Blood may pass into the lungs and be coughed
up. Swallowing is usually difficult and painful, especially in
fracture of the hyoid bone. There is also pain on speaking, the voice
is husky and indistinct, and spasmodic coughing is common. When blood
has entered the air-passages there i