300 CONTAGIOUS PI.EURO-PNEUMONIA 



typical course and by its sporadic and sudden appearance 

 and, anatomically, by the fact that the parts which have 

 undergone hepatization are practically all of the same age and 

 by the interstitial lung tissue and pleurae being but slightly 

 involved. Nocard states that in exceptional cases pleuro- 

 pneumonia may run a very acute course and show hepatiza- 

 tion of equal ages. 



2. Tuberculosis. This disease cannot be positively distin- 

 guished clinically from pleuro-pneumonia. Tuberculin may be 

 used as a diagnostic agent, although it is not at all certain 

 that animals which have suffered for son:e time from pleuro- 

 pneumonia do not react to tuberculin. After all, an anatomi- 

 cal examination is the only real test. Tuberculosis and con- 

 tagious pleuro-pneumonia have occasionally appeared simul- 

 taneously in the same animal. See description of lesions in 

 tuberculosis. 



3. Traumatic pneumonia or pneumonia due to foreign 

 bodies may exhibit the .same .symptoms as pleuro-pneumonia. 

 Evidence, during life, of changes in the heart caused by trau- 

 matic carditis will be conclusive in making the differentiation. 



4. Broncho or interstitial pneumojiia . In making a diag- 

 nosis between contagious pleuro-pneumonia, ba.sed on the lung 

 lesions alone, it should always be borne in mind that the entire 

 lungs should be subjected to examination. Attention should 

 be given to signs indicating injury to the chest wall, to the 

 possible presence of foreign bodies and to severe inflammation 

 of the air passages which may result from the aspiration of 

 irritant or corrosive fluids. Where these agents may be 

 excluded special attention should be paid to the condition of 

 the pleura and to the distribution of the disease, careful notes 

 being made of the lobes involved. Next in order come the 

 peculiar perivascular and interlobular thickening and the 

 thrombosis of the veins. Care should be taken not to con- 

 found mere clots with adhesive thrombi. In acute pleuro- 

 pneumonia, after death, the arteries are usually distended 

 with clots. The different features of the hepatized and 

 oedematous portions of the lung tissue should be carefully 

 noted. Lastly, the peculiar exudation and infiltration in the 



