THE RESPIRATORY SYSTEM. 483 



hindrance to the exit of blood through the pulmonary vein, such as mi- 

 tral stenosis or insufficiency, or to enfeeblement of the ventricular con- 

 tractions, as in fatty degeneration of the heart muscle or interstitial myo- 

 carditis. In the last hours of life the feeble action of the heart disposes 

 to pulmonary congestion. The position of the body upon the back in 

 bed favors an accumulation of blood in the posterior portions of the 

 lungs hypostatic congestion. Hypersenric lungs are in varying degrees 

 darker and heavier than normal ; an unusual amount of blood flows from 

 the cut surface. CEdeniatous fluid is often also present. Bed blood 

 cells often pass through the capillary walls in hypersemia and these with 

 more or less exfoliated epithelium may be found in the air vesicles. 



FIG. 267. CHRONIC CONGESTION OF THE LUNG. (BROWN INDURATION.) 



Showing dilated capillaries of the walls of the air vesicles and basmatogenous pigment in the exfoliated 

 epithelial cells of the air vesicles. 



Chronic Congestion, In prolonged hypera3mia of the lungs, notably in 

 connection with lesions of the mitral and aortic valve, or degeneration 

 or dilatation of the left ventricle, the veins and capillaries, especially 

 the capillaries, become permanently distended, pouched, and elongated, 

 so that they often stretch in loops into the air spaces (Fig. 267). Eed 

 blood cells find their way from the contorted vessels by diapedesis or small 

 haemorrhages into the air vesicles or interstitial tissue of the lung. Here 

 decomposition of the haemoglobin leaves brownish pigment particles which 

 may remain free or be taken into cells. In the air vesicles the epithelial 

 cells usually desquamate in considerable numbers, and take up the 

 pigment in varying amount. This pigment gives to the lungs a peculiar 

 brownish pink or salmon color. The appearance of these lungs may be 

 modified by hsemorrhagic infarctions, by pre-existing emphysema or 

 oedema, or by exudative inflammation. Associated with these changes 



