CHRONIC INTERSTITIAL PNEUMONIA 143 



and gradually fall as the disease decreases and the animal goes on to 

 convalescenre. 



Course and Prognosis. — The course of catarrhal inflammation of the 

 lungs is rarely less than three weeks, and is often prolonged over three 

 months, with varying degrees of intensity. Traumatic pneumonia is the 

 only form of the disease that runs its course quickly. 



The evidences of termination of the disease arc: Recovery by 

 resolution, in which the inflammatory products, which fill the smallest 

 l)i'onchia and the alveoli, are changed into a form of emulsion and are 

 either reabsorbed or coughed up, or develop into a secondary disease, 

 for instance, chronic interstitial inflammation of the lung or, in rare cases, 

 the formation of purulent gangrenous centres. Third, death, which may 

 occur at any stage of the disease; in the early stages, as a conseciuence 

 of great extension of lobular pneumonia or at any time as a result of 

 cedema of the lungs, this is observed in very young animals that are 

 very weak, particularly in the pulmonarj' form of distemper, but it may 

 also occur in very old debilitated animals. Traumatic pneumonia, if 

 it is acute, generally results fatally and little or nothing can be done 

 to produce a favorable result. 



Chronic Interstitial Pneumonia. 



{Chronic Induration of the Lungs; Cirrhosis of ihe Lungs; Phthisis.) 



When the disease terminates in this pathological condition we find 

 an inflammatory deposit in the interlobular and interstitial connective 

 tissue. This deposit compresses the alveoli and small bronchia, and 

 they lose their functions and are finally absorbed, and on section of the 

 affected portion of the lung it is found to be coarse, rough, and irregu- 

 lar on its surface, the tissue varying from yellow to yellowish-red in 

 color and the lobules surrounded by connective tissue. The bronchia 

 surrounding the affected portion are distended and pocket-shaped, 

 and there are also a certain number of spots of localized emphysema. 



The clinical course of the disease shows very little fever, but the 

 animal is never entirely restored to health; the respirations are short, 

 labored, and with a quick, weak cough. The affected animal becomes 

 emaciated, the condition is complicated wdth dropsical effusions, and it 

 finally dies from exhaustion. 



In some cases of lobular inflammation of the lungs the inflamed 

 portions form abscesses, or we may find portions of the lung that are 

 gangrenous. These terminations depend on the nature of the irritant, 

 and generally occur after traumatic pneumonia (foreign bodies). A^ hen 

 suppuration commences in the alveoli, an abscess is formed and a pear- 

 shaped body is found in the centre of the infiltrated lobule, and sur- 



