ory position produces in some cases an elevation of the
superior thoracic aperture simulating laryngoptosis (Bibliography r,
pp. 468, 594).

_Compression Stenosis of the Trachea and Bronchi_.--Compression of the
trachea is most commonly caused by goiter, substernal or cervical,
aneurysm, malignancy, or, in children, by enlarged thymus. Less
frequently, enlarged mediastinal tuberculous, leukemic, leutic or
Hodgkin's glands compress the airway. The left bronchus may be
stenosed by pressure from a hypertrophied cardiac auricle. Compression
stenosis of the trachea associated with pulmonary emphysema accounts
for the dyspnea during attacks of coughing.

The endoscopic picture of compression stenosis is that of an
elliptical or scabbard-shaped lumen when the bronchus is at rest or
during inspiration. Concentric funnel-like compression stenosis, while
rare, may be produced by annular growths.

_Treatment of Compression Stenoses of the Trachea_.--If the thymus be
at fault, rapid amelioration of symptoms follows roentgenray or radium
therapy. Tracheotomy and the insertion of the long cane-shaped cannula
(Fig. 104) past the compressed area is required in the cases caused by
conditions less amenable to treatment than thymic enlargement.
Permanent cure depends upon the removability of the compressive mass.
Should the bronchi be so compressed by a benign condition as to
prevent escape of secretions from the subjacent air passages,
bronchial intubation tubes may be inserted, and, if necessary, worn
constantly. They should be removed weekly for cleansing and oftener if
obstructed.

_Influenzal Laryngotracheobronchitis_.--Influenzal infection, not
always by the same organism, sweeps over the population, attacking the
air passages in a violent and quite characteristic way. Bronchoscopy
shows the influenzal infection to be characterized by intense
reddening and swelling of the mucosa. In some cases the swelling is so
great as to necessitate tracheotomy, or intubation of the larynx; and
if the edema involve the bronchi, occlusion may be fatal. Hemorrhagic
spots and superficial erosions are commonly seen, and a thick,
tenacious exudate, difficult of expectoration, lies in patches in the
trachea. Infants may asphyxiate from accumulation of this secretion
which they are unable to expel. The differential diagnosis from
diphtheria is sometimes difficult. The absence of true membrane and
the failure to find diphtheria bacilli in smears tak