PLEUROPN EU MON I A. 



[Description of plates.] 



Plate XXX. The dorsal, or upper, surface of the lungs of the ox reduced to 

 one-sixth of the natural size : a. a', the right and the left principal lobes. These 

 are the largest and are situated iwsteriorly, resting upon the diaphragm; ft, b', 

 the ventral lobes, situated between the principal lobes; and c, c', c" the most 

 anterior, or cephalic, lobes. The right anterior is divided into two lobes (c, c'), 

 the left is single {c")", d, trachea, or windpipe. 



Those portions of the lung tissue lying outside of the dotted lines are the ones 

 most commonly affected in the ordinary types of pneumonia. In the majority 

 of the lungs examinefl in the laboratoi-y of the bureau which were affected with 

 contagious pleuropneumonia the principal lobes (o, a') were primarily affected. 



Plate XXXI. The ventral, or middle, lobe of the right lung affected with col- 

 lapse and beginning bronchopneumonia. The light yellowish ix>rtions repre- 

 sent healthy lung tissue; the red represents the disease. It will be noticed 

 that the lines between the lobules are quite faint, indicating little or no inflam- 

 mation of the connective tissue between the lobules. The healthy lung tissue 

 is seen to be raised above the level of the diseased portion. In contagious 

 pleuropneumonia the exact reverse is the case, the diseased portions being very 

 much larger than the healthy. 



Plate XXXII. Appearance of a cow's lung affected with contagious pleuro- 

 pneumonia when sections or slices are made of it and cut surfaces examined. 

 Fig. 1. Transverse section through the right principal lobe in a case of acute 

 pleuropneumonia. The area drawn includes the air tubes, veins, and arteries 

 and illustrates the great thickening of the interlobular connective tissue into 

 broad whitish bands and of the walls of the air tubes, veins, and arteries; a, 

 air tube cut obliquely; a', air tube cut directly aci'oss; ft, arteries cut across; 

 c, large vein completely occluded by a thrombus, or plug, formed during life. 

 The great thickening of the walls of the artei^y and vein in this disease is 

 especially brought out by stating that in the healthy lung they are so thin as 

 to be easily overlooked. Fig. 2. Transverse section of the principal lobe in a 

 case of acute pleuropneumonia, illustrating the different kinds of hepatization 

 or consolidation of the lung. These are indicated by the different colors from 

 dark red to reddish yellow. This variation of color is regarded by some as 

 the real marbling characteristic of pleuropneumonia, while the whitish bands 

 penetrating the lung tissue in all directions constitute the true marbling accord- 

 ing to other observers. 



Plate XXXIII illustrates what are called infarctions in pleuropneumonia. 

 The right half of the figure shows nearly nomial lung tissue. The left repre- 

 sents a blackish mass in which the lung tissue is filled with blood and solidified. 

 This is caused by the plugging of the vein carrying away the blood from this 

 portion. The heart forces the blood through the artery into the tissue at con- 

 siderable pressure, but, owing to the fact that its return is prevented, the minute 

 blood vessels rupture and the air vesicles become distended with blood, which 

 coagulates and causes the firmness of the tissue. 

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