DISEASES OF THE HOG. 119 
fore remain distended. The lungs are very light and 
do not sink in water as in the sound state. It cre- 
pitates tess upon pressure, has a firm feeling, and 
pits under the finger. The surface of the lung will 
be found uneven on account of some parts of it: be- 
ing more distended than others. Some of these pro- 
jections may be single and not larger than a pea; 
that these are distended air cells is proved by the 
circumstances. that they cannot be moved from 
place to place under the pleura by pressure. When 
a diseased lung is cut into the air cells are found to 
~be in various degrees enlarged generally to about 
the size of a millet seed, sometimes to that of a 
hazel nut and sometimes larger. The small ones 
are merely dilated vesicles, the larger are pro- 
duced by the rupture of the intervening coats and 
the gradual absorption of the torn walls of the 
cells. The dilatation may affect only one or a few 
cells or may occupy isolated spots as single lobules; 
for example, while others remain unchanged or 
may extend to large and continuous portions of the 
parenchyma it may be confined to one lung or both 
may be affected. When only one lung is affected 
it will be found to be so much larger than the other 
that it will displace the mediastinum and heart. 
The dilatation most frequently affects the anterior 
and its borders than elsewhere. The edges of the 
tubes are sometimes fringed with the projecting 
dilated vesicles of different sizes. The small bron- 
chial tubes are usually also dilated in the emphyse- 
matous parts. In consequence of a diminished sup- 
ply of blood to the affected parts of the lung it will 
