372 DISEASES OF CATTLE. 



faction. The softened mass is finally absorbed and the walls of the 

 cyst, or capsule around it, gradually collapse and form a cicatrix. 

 This favorable termination takes place only when the dead mass is not 

 too large. It may, however, involve over a half of one of the large 

 lobes. Under such circumstances recovery is improbable. A more 

 favorable termination is the abundant growth of fibroxis tissue around 

 and into the hepatized masses. The formation of fibrous tissue may 

 extend to the pleura, or lung covering, and cause firm adhesion of the 

 lungs to the chest wall and to the pericardium, or heart case. 



The same peculiar inflammatory changes which take place between 

 the lobules of the lung and arnund the bronchi and vessels may invade 

 the pleural cavity, cause extensive membranous and spongy deposits 

 on the pleura and firm deposits around the heart and large arteries, 

 the gullet, and windpipe. 



These are the main features of the lung disease caused by contagious 

 pleuro-pneumonia. In the typical acute cases there are a sufficient 

 number of peculiarities to enable us to make a positive diagnosis. 

 There are, however, many cases in which the disease is restricted to 

 small areas, or to the interlobular tissue, or in which the changes are 

 as yet imperfectly developed, or else so far advanced that doubts may 

 arise as to the true nature of the affection. In such cases all obtain- 

 able facts, including the history of the case, the symptoms during life, 

 and the pathological changes observed on postmortem examination 

 must be taken into consideration. Only one who has made a careful 

 study of the disease is fitted to decide in such cases. 



Other kinds of lung disease may be confounded with pleuro-pneu- 

 monia because of certain features common to most lung diseases of 

 cattle. The inflammation of the connective tissue between the lobules 

 is not infrequently observed in so-called interstitial pneumonia and 

 may lead to the formation of whitish bands intersecting the lung tissue 

 in various directions. On the cut surface these bands may give rise 

 to a decidedly marbled appearance. Again, in traumatic pneumonia, 

 due, as its name implies, to 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 pleuro-pneumonia in its retrogressive 

 stages when it is confined to a small portion of lung tissue. The fill- 

 ing up of the interlobular spaces with fibrin and connective tissue of 

 inflammatory origin is not thus limited to pleuro-pneumonia, but may 

 appear in a marked degree in other lung diseases. It must not be 

 inferred from this statement that these interlobular changes are nec- 

 essarily the same as those in pleuro-pneumonia, although they may 

 appear the same to the naked eye. We simply note their presence 

 without discussing their nature. 



In general the distinction between pleuro-pneumonia and broncho- 

 pneumonia isrnot difficult to make. In the latter disease the pnemno- 



