376 DISEASES OF CATTLE. 



Though unknown in this country, the importance of having near at 

 hand a few definite facts concerning this disease, should it ever reach 

 our shores, will be at once appreciated. A knowledge of such facts 

 may aid in an early recognition of the disease. It must not be for- 

 gotten, od the other hand, that a superficial knowledge of diseases, 

 such as the layman may gain through reading, not infrequently leads 

 to confounding comparatively harmless, noninfectious maladies with 



PLEURO-PNEUMONIA. 



[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 posteriorly, resting upon the diaphragm; b, b', the 

 ventral lobes, situated between the principal lobes, and c, c', c' ' , the most anterior, 

 or cephalic, lobes; c, c',c". anterior, or cephalic, lobes. The right anterior is divided 

 into two lobes (e, 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 examined in the laboratory of the Bureau, which were affected with 

 contagious pleuro-pneumonia, the principal lobes (a, a') were primarily affected. 



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

 lapse and beginning broncho-pneumonia. The light yellowish portions represent 

 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 inflammation 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 pleuro-pneumonia 

 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 pleuro- 

 pneumonia. The area drawn includes the air tubes, veins, and arteries, and illus- 

 trates 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 across; b, arteries cut across: c, large vein com- 

 pletely occluded by a thrombus, or plug, formed during life. The gre.at thicken- 

 ing of the walls of the artery 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 pleuro-pneumonia, 

 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 varia- 

 tion of color is regarded by some as the real marbling characteristic of pleuro- 

 pneumonia, while the whitish bands penetrating the lung tissue in all directions 

 constitute th-:- true marbling according to other observers. 



Plate XXXIII illustrates what are called infarctions in pleuro-pneumonia. 

 The right half of the figure shows nearly normal lung tissue. The left represents 

 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 considerable pres- 

 sure, 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. 



