190 DEFORMITY AND STENOSIS OF THE TRACHEA. 
bent inwards, or flattened so that the lumen forms merely a narrow 
fissure. 
Gurlt saw a dog with marked flattening of the air tube. Harms and Hagen 
note similar cases in cows. Johne describes two instances of dilatation in 
horses, one about 24 inches in length, and a similar condition was 
recorded by Bartenstein. Yegezzi found the dorsal surface of the air tube of 
a horse presenting a furrow produced by bending inwards of the ends of the 
cartilages and rupture of the inter-annular ligament. In this furrow lay the 
oesophagus, carotid, vagus, and sympathetic. Eberbach describes a horse in 
which dyspnoea w r as caused by compression of the trachea, due to a large 
sarcoma. 
The intact condition of the mucous membrane and the extension of the 
change throughout the trachea shows the disease to be congenital. Com¬ 
pression, with narrowing of the trachea, may also result from goitre, 
from enlargement of the bronchial glands, or from tumour formation. 
Johne relates such a case in a giraffe, and Dietrich in a foal which had 
died with symptoms of suffocation. Between the first pair of ribs was 
a diseased gland, which had compressed the trachea and caused 
suffocation. 
Stenosis of the trachea is not an infrequent result of tracheotomy, 
especially in foals, or where the tube, worn for a long period, does not fit 
well. Chronic perichondritis resulting from the continued irritation, 
induces formation of cicatricial tissue, which sometimes ossifies, and 
narrows the lumen of the tube, firstly by pressing on it, and afterwards 
by contracting around it. Thus Tiede found the trachea narrowed to the 
size of a goose quill. Stenosis is not always a result of unskilfulness in 
performing tracheotomy or selecting a tube; stenosis sometimes recurs 
in horses in which tracheotomy has been performed below a previous 
contraction, it therefore seems likely that some animals are predisposed 
to such conditions. 
The symptoms of injury to the trachea are difficulty in breathing, and 
emphysema on the neck, with localised inflammation, swelling, and pain. 
The degree to which the lumen of the tube is narrowed in consequence 
of haemorrhage, dislocation of its cartilages, or inflammatory swelling, 
determines the extent of the respiratory disturbance, which may become 
so great as finally to produce suffocation. In other cases a loud sound 
is heard both during inspiration and expiration. Very slight changes in 
the trachea are sufficient to produce it. Sometimes the noise may be 
increased or diminished by pressing on a particular part of the trachea. 
Laying the ear on the wind-pipe, the position of the stenosis may be 
more exactly fixed, but this method does not always prevent mistakes. 
During the next few days the emphysema usually spreads over the body, 
especially when coughing exists, but disappears later, generally without 
bad results. 
