MORBID ANATOMY 141 
The inflamed areas occasionally contain centres of 
suppuration, from which copious pus will exude upon 
incision. The small bronchi and bronchioles contain a 
frothy greyish or even blood-stained pus which mechani- 
cally impedes the entrance and egress of inspired air, 
and assists in the production of dyspneea.- 
In some cases, particularly in puppies, the fines 
become swollen or generally enlarged, darker, very 
moist and prominent, and a serous exudate flows from 
the cut surface in great quantity. This is the condition 
of edema, which consists in extravasation of serum from 
the blood-vessels into the alveoli, bronchioli, and bronchi, 
which it almost completely fills, thus excluding large 
portions of the lung from free circulation of blood and 
air, and producing in fatal cases cyanosis and death from 
asphyxia in from twelve to twenty-four hours. 
As death approaches, profuse discharges of this 
liquid (rendered opaque by admixture with pus, and 
pink or red from the presence of erythrocytes) escape 
from the nostrils, an abundance of it also being found 
whipped to foam in the trachea. 
Pleura.—More or less serous exudate may be present 
in. the thoracic cavity, particularly where pleurisy has 
been a complication ; and those portions of the pleura 
which cover the affected lung often become the seat of 
pathological change. The membrane may only show a 
roughening on its surface, or it may be covered with 
fibrinous lymph, which may cause the visceral pleura to 
adhere to the parietal, though this is rare. Congestion 
of the parietal pleura is sometimes observed, and it may 
even show a lymph deposit. 
The nature and colour of the exudate found in the 
pleural cavity will depend upon the acuteness and type 
of the pulmonary disease; thus it may be hemorrhagic, 
purulent, putrid and greenish, or serous. 
