SWINE PLAGUE 53 
Two kinds of pneumonia are encountered, namely, lobar and 
catarrhal or broncho-pneumonia. In the former the vesicular portion 
of the lung substance is chiefly affected; in the latter the smaller 
bronchioles are primarily attacked and the alveoli secondarily. In 
croupous-pneumonia, there is, following the stage of congestion, an 
emigration of red blood corpuscles, some leucocytes, and an exudate 
of fibrm into the air spaces. These elements are firmly matted 
together by the coagulating fibrin, making the diseased lung firm to 
Fic. 5. 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 AD- 
VANCED 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. 
the touch. In broncho-pneumonia the catarrhal condition of the 
smaller air tubes makes them impervious 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. Subse- 
quently 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 circulation we may have more or less 
