MORBID ANATOMY 



79 



the alveoli and the distended condition of the capillary net- 

 work. Subsequently the inflammation extends into the alveoli, 

 which then become distended with cellular masses. 



The nature of the lung disease will depend more or less 

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

 by way of the air tubes it will appear perhaps as a broncho- 

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

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



FiG. II. Right lung of pig. The stippled portion is usually 

 involved in cases of infectious pneumonia or swine plague, (b) ventral 

 lobe, {c) cephalic lobe, {a) principal lobe. The ventral lobe is usually 

 the seat of the more advanced disease and consequently the first to become 

 hepatized. The cephalic portion of the principal lobe {x") is usually 

 hepatized and the remaining portion deeply reddened. / 



tion (embolic pneumonia). If it enters by way of the pleura, 

 the virus will creep along the interlobular and peribronchial 

 tissue before it invades the parenchyma proper. 



In natural infection of swine plague, bacteria seem to 

 enter the lung tissue chiefly by way of the air tubes. At the 

 same time it is not improbable that occasionally they may 

 enter the serous cavities first, /. e. , invade the pleural cavities 

 and thence the lungs. This probability is shown by inocula- 



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