PULMONARY EMPHYSEMA. 359 



cachectic. Many suffer from the disease and yet remain in fair bodily 

 condition. 



On i)ost-mortem examination the hmgs are found not to collapse, 

 having lost their elasticity, and are of a yellowish-white colour, which is 

 only seen in this disease. On section the pulmonary tissue appears 

 dense, hard, and of a fibrous and lardaceous character. At various 

 points nodules with fibrous envelopes and caseous, yellowish or greenish 

 contents are found. 



When the caseous nodules are near the surface the pleura may be 

 chronically inflamed and thickened. The liver and kidney frequently 

 contain caseous lesions. 



Diagnosis. The diagnosis becomes easy after the first post-mortem 

 examination, for the lesions discovered cannot be mistaken for those 

 of parasitic broncho-pneumonia, degenerated pulmonary echinococcosis 

 or tuberculosis. In the living animal, on the contrary, the diagnosis 

 is extremely difficult. 



Prognosis. The prognosis is grave. No special method of treat- 

 ment is known. 



PULMONARY EMPHYSEMA. 



Pulmonary emphysema, i.e., exaggerated dilatation of the pulmonary 

 tissue by air, is not uncommon in the bovine species, and occurs under 

 the two classical forms — (1) alveolar or intra-lobular emphysema limited 

 to dilatation of the alveoli ; and (2) interlobular emphysema, produced 

 by the entrance and diffusion of air in the interlobular spaces in con- 

 sequence of rupture of the lobules. 



These two forms are very frequently associated : — 



(1.) Emphysema by dilatation usually begins in the right pretracheal 

 lobe ; also in the cardiac and even in the posterior lobes. 



(2.) Interlobular emphysema begins in the same regions, but it 

 spreads readily in a backward direction, remaining interstitial ; or, on 

 the other hand, becoming sub-pleural at the periphery of the lung. 



In both cases the pulmonary tissue is pale, the blood-vessels are 

 partially obliterated by compression ; circulation and aeration of the 

 blood are impeded— hence the appearance of the disturbance noted. 



Causation. Emphysema is seen in adult working oxen ; also, and to 

 an even greater degree, in aged cows. It is produced by excessive strains 

 in draught, or more often by the paroxysms of coughing so common 

 during simple or parasitic bronchitis, broncho-pneumonia, pneumonia, 

 chronic broncho-pneumonia, etc. Successive gestations also produce it. 



All these pathological conditions also interfere with the nutrition of 

 the bronchial mucous membrane, particularly of its deep-seated muscular 

 layer, which is then incapable of regulating the distribution of air ni the 



