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 less 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 



