372 DISEASES OF CATTLE. 



honeycombed and the spaces filled with yellowish fluid (serum) or 

 they may be uniformly solid. It will also be noticed that the space 

 iimnciliately outside of and around the artery, vein, and air tube is 

 similarly broadened by fibrinous deposits. Some authorities look 

 upon these bands as constituting the so-called " marbling "' of pleuro- 

 pneumonia. 



In addition to these changes which have taken place in the connec- 

 tive tissue between the lobules, the lung tissue itself may be mark- 

 edly altered. Certain areas of the cut surface may be very firm in 

 texture and of a brownish-red color. The cut surface is granular or 

 roughened, not smooth to the eye. Other areas equally firm may be 

 more grayish yellow and still others may be blackish. (PI. 

 XXXII.) Besides these areas which represent solidified (hepatized) 

 lung tissue there may be others which approach the normal lung tis- 

 sue in color, are soft, and float in water. From these a milky, 

 purulent fluid may often be expressed. These different shades are 

 I'eiDresented in Plate XXXI, fig. 2, within a small compass. Some 

 authorities are inclined to consider these variations in color on the 

 same cut surface as the co-called marbling of pleuropneumonia. It 

 matters not whether we regard the bands Ijetween the lobules or the 

 varying shades of the lobules themsehes as the marbling, provided 

 either or both are peculiar to contagious pleuropneumonia. If we 

 examine the blood vessels ap^Dearing on such cut surface they will 

 usually be found plugged within the firmly hepatized regions. The 

 artery contains a dark, soft, removable clot, the vein a grayish-pink, 

 granular, fragile plug (thrombus), which adheres firmly to the wall 

 of the vein, and if this is slit open, indications of a diseased condition 

 of the inner coat will be jeadih^ detected. When large regions of the 

 lung tissues are hepatized, the main air tube and its Ijranches are 

 usually filled with grayish, cylindrical branched masses of fibrin that 

 are easily removed, as they do not adhere to the mucous membrane. 



The A'iews of pathologists differ as to the nature of the earliest 

 changes in pleuropneumonia, and it is not Avithin the '^cope of this 

 work to present controverted or im]ierfectly develoi)ed theories. In 

 the foregoing description we have taken as a type the acute pleuro- 

 l^neumonia in its fully developed phase, which can scarcely be mis- 

 taken for any other disease, "\^"e ha^•e seen that there is an inflam-' 

 matory condition of the connective tissue between the lobules, result- 

 ing in the exudation of coagidable lymph. This inflammation is 

 equally marked around the blood vessels and air tnlies. It leads to 

 inflammatory changes in the inner wall of the veins, and these cause 

 the deposition of thrombi or plugs in the vessels, which prevent the 

 return of the blood. The blood pumped into the lung tissue through 

 tlie artery, but unaljle to get <iut by way of the vein, leaves the mesh- 

 work of capillaries around the air vesicles, enters the latter, and pro- 



