146 MANUAL OF EQUINE MEDICINE. 



some cases involving the whole thickness of the bronchial 

 walls, and leading to infiltration and induration of the con- 

 nective-tissue surrounding them. 



In some instances the inflammatory process ends in 

 ulceration, and ulcerated patches of varying size may be ob- 

 served after death. 



When the small tubes are especially involved, the thicken- 

 ing of the mucous membrane encroaches more seriously on 

 the channels of the affected tubes, and their secretions tend 

 to accumulate in them, and block up their lumina entirely. 

 In cases where the secretion is abundant or viscid, diffuse 

 or circumscribed patches of collapsed or condensed lung 

 tissue of varying extent are of frequent occurrence. 



This condition (atelectasis) results from the plugging of 

 the bronchi with inspissated secretion or pus. These 

 patches may be seen after death on the surface of the lung, 

 as depressed areas of a dark violet hue, the surrounding 

 parts being of a light pink colour, and either healthy or 

 emphysematous. 



The collapsed portions are less crepitant than normal 

 lung, but not so much as hepatized lung, and they resemble 

 foetal lung, sinking slowly in water. 



On cutting into the lungs, the large and small tubes, and 

 sometimes the trachea, contain a quantity of secretion. 

 This condition, as well as the collapse, is usually limited to 

 the anterior lobes of the lung, and rarely affects the large 

 lobules except by extension. The fluid in the tubes in the 

 earlier stage, after that of arrested secretion, is thin and 

 serous, but afterwards becomes thick and yellow. In the 

 trachea it is frothy, more or less, and is abundant in the 

 small tubes, from which yellow matter may be expressed. 



If a portion of the collapsed tissue be cut into, opaque 

 serous blood-stained fluid, sometimes intermingled with 

 purulent secretion, exudes from the cut surface. After a 



