54 



SWINE PLAGUE 



the smaller bronchioles are said to be primarily affected and 

 the vesicular portion or alveoli secondarily. In croupous 

 pneumonia, there is, following the stage of congestion, an 

 emigration of red blood corpuscles, some leucocytes and an 

 exudate of fibrin into the air spaces. These elements are 

 firmh' matted together by the coagulating fibrin, making the 

 diseased lung firm to the touch. In broncho-pneumonia the 

 catarrhal condition of the smaller air tubes makes them imper- 

 vious to air. The lung tissue which they supply is gradually 

 emptied of air and assumes the appearance of red flesh, owing 

 to the collapse of the walls of the alveoli and the distended 

 condition of the capillary network. vSubsequently the inflam- 

 mation extends into the alveoli, which then become distended 

 with cellular masses. 



Fig. 7. Portion of hmg showing emphysema. 



The nature of the lung disease will depend more or less 

 upon the mode of entrance of the virus. If it entered only 

 by w^ay of the air tubes it will appear perhaps as a broncho- 

 pneumonia. If it enters the lung tissue through the circu- 

 lation we may have more or less scattered centers of hepatiza- 

 tion'fembolic pneumonia.) If it enters by way of the pleura. 



