158 MANUAL OF EQUINE MEDICINE. 



(B.) Abscess. — This is a rare termination. When one or 

 more abscesses are formed they may discharge themselves 

 by the air-tubes, or may undergo caseous or calcareous de- 

 generation. 



(C.) Gangrene. — This is a still rarer termination. It 

 is due to extensive formation of coagula in the pulmonary 

 and bronchial vessels, together with considerable haemor- 

 rhage into the pulmonary tissue, and is predisposed to by 

 malhygienic conditions to which the animal may have been 

 exposed. 



(D.) Chronic Pneumonia. — If the inflammation do not sub- 

 side, and the exuded liquid become absorbed, the alveolar 

 walls gradually become involved, and thickened by fibro- 

 nucleated growth. 



2. PATkoLOGICAL CHANGES IN CATARRHAL OR 

 BRONCHO-PNEUMONIA.— The inflammation of the pul- 

 monary tissue is in this form always associated with catarrh 

 of the bronchi. 



Broncho-pneumonia may be caused firstly by the collapse of 

 the lung-tissues from inflammation of the bronchial mucous 

 membrane ; secondly, by direct extension of the inflamma- 

 tion from the bronchi into the air-cells ; and lastly, the in- 

 flammation may originate in the air-vesicles themselves 

 before the bronchi are attacked. In catarrhal pneumonia, 

 the inflammatory products which fill the alveoli consist very 

 largely of cells derived from the epithehum of the alveoli 

 and from the bronchial mucous membrane. 



Exudation and emigration play a much less prominent 

 part in the process than they do in croupous pneumonia. 



This form has been termed catarrhal pneumonia, from 

 the preponderance of epithelial products, and from the 

 association of the pulmonary with the bronchial inflam- 

 mation. 



Eesolution is less readily effected in broncho-pneumonia 



