374 DISEASES OF CATTLE. 



traumatic pneumonia, caused, as its name implies, by the entrance 

 of foreign bodies into the lung tissue, generally from the paunch, 

 the connective tissue around the place of disease becomes inflamed 

 and thickened, and the disease itself may simulate pleuropneumonia 

 in its retrogressiA'e stages Avhen it is confined to a small portion of 

 lung tissue. The filling up of the interlobular spaces with fibrin 

 and connective tissue of inflammatory origin is not thus limited to 

 pleuropneumonia, but may appear in a marked degree in other lung 

 diseases. It must not be inferred from this statement that these 

 interlobular changes are necessarily the same as those in pleuro- 

 pneumonia, although to the naked eye they may appear the same. 

 We simply note their presence without discussing their nature. 



In general, the distinction betAveen pleuropneumonia and broncho- 

 pneumonia is not difficult to make. In the latter disease the pneu- 

 monia generally invades certain lobes. The disease attacks the smaller 

 lobes in their lowest portions first and gradually extends upward, i. e., 

 toward the root of the lung or the back of the animal and backward 

 into the large principal lobes. Again, both lungs in advanced cases 

 are often symmetrically affected. In contagious pleuropneumonia 

 the large principal lobe of one side is most frequently affected, and a 

 symmetrical disease of both lungs is very rare, if, in fact, it has ever 

 been observed. The lung tissue in bronchopneumonia is not enlarged, 

 but rather more contracted than the normal tissue around it. This is 

 well illustrated in Plate XXX. Normal, air-containing lobules may 

 be scattered among and around the hepatized portion in an irregular 

 manner. In pleuropneumonia the diseased and healthy portions are 

 either sharply divided off, one from the other, or else they shade into 

 each other by intermediate stages. 



The hepatized lung tissue in bronchopneumonia when the cut sur- 

 face is examined is usually of a more or less dark flesh color with 

 paler grayish-yellow dots regularly interspersed, giving it a peculiar, 

 mottled appearance. In the more advanced stages it becomes more 

 firm, and may contain nodular and firmer masses disseminated 

 through it. The air tubes usually contain more or less soft, creamy, 

 or cheesy pus or a turbid fluid quite different from the loose, fibrin- 

 ous casts of acute pleuroi^neumonia. The interlobular tissue may or 

 may not be affected. It sometimes contains loose, fibrinous plugs, or 

 it may be greatly distended w^ith air, especially in the still normal 

 portions of the lung. The pleura is seldom seriously diseased. If 

 we contrast with these features the firm dark-red hepatizations, the 

 plugging of the veins, the extensive interlobular dejjosits, and the 

 well-marked pleuritis in pleuropneumonia, there is little chance for 

 confusion between well-developed cases of these two lung diseases. 



It should not be forgotten, however, that the lesions of the disease 

 known as contagious pleuropneumonia nuiy be confined to the serous 



