8o SWINE PLAGUE 



tion in which intravenous injections produced exudative pleu- 

 ritis and pneumonia of the most dependent portions of the 

 lungs covered by the pleural exudate. It is not improbable 

 that even in the natural disease the bacteria which have 

 gained access to a portion of the lung tissue by way of the air 

 tubes reach the pleura covering this portion, and may then by 

 this route invade other portions of the lungs. It may be that 

 in this way a pneumonia originally single may become double. 

 It has been observed that the first pneumonic infiltration of 

 the principal lobe was at the point of contact with the dis- 

 eased ventral lobe, and that the resting of a lobe against an 

 inflamed serous surface, such as the pericardium, caused a 

 pneumonic infiltration at the point of contact. 



The character and seat of the lung lesions are somewhat 

 variable. It is difficult to find two lungs exactly alike so far 

 as gross appearances go. This to be sure may be due largely 

 to the fact that animals die in different stages of the disease. 

 Yet there are differences evidently not dependent on this fact, 

 which must be left for special pathological investigation. 



In general the cephalic (anterior) half of a swine- plague 

 lung is hepatized, of a dark-red or grayish-red color and firm 

 to the touch. The pleura is more or less thickened and 

 opaque, and possibly covered with easily removable, friable, 

 false membranes. In the more recently affected regions a 

 faint but quite regular, delicate mottling with yellow is 

 observed to shine through the pleura when not thickened. 

 These minute hazy, yellowish dots usually occur in groups of 

 four. Occasionally whitish or yellowish patches varying 

 much in size are seen, perhaps more frequently in the ventral 

 lobes. These correspond to homogeneous dead masses of lung 

 tissue. 



When such lungs are cut open, the section presents much 

 the same appearance, both as regards color and mottling, as 

 when viewed from the surface, excepting that the details are 

 less distinct. In some cases, in the most recently invaded 

 territories in the principal lobe and nearer the dorsum in the 

 other lobes, the dark or grayish-red cut surface shows grayish 



