338 DISEASES OF THE RESPIRATORY ORGANS. 



The lungs are heavy and somewhat larger than normal. 

 On section they are dark red in color, and on pressure a 

 brownish-red serum exudes, frothy from admixture of air 

 oedema. In other and more chronic cases the lung-tissue is 

 dry and indurated. 



Microscopically, in cases in which the brown induration is 

 marked, there is considerable increase in the connective tissue 

 of the lung ; the pleura, interlobular septa, and alveolar walls 

 are thickened and pigmented. The alveolar walls have a 

 beaded appearance, due to the passive engorgement of the 

 capillary bloodvessels. Within the air-spaces are red blood- 



FIG. 148. 



Brown induration of lung, d, prominent capillaries in alveolar wall ; a, cells con- 

 taining pigment in lumen of alveolus; 6, c, alveolar epithelium. X 250 

 (Schmaus). 



corpuscles, numerous leukocytes, and desquamated epithelial 

 cells many of which contain pigment derived from the 

 altered red blood-corpuscles which they have englobed and 

 digested (see Fig. 148). Later, these cells having been taken 

 into the lymphatic system, the pigment is thus distributed. 



(Edema of the lungs may also result from active congestion, 

 produced by inhalation of very hot or cold air, irritating 

 gases, etc. Microscopically the alveoli are found to contain a 

 few leukocytes, desquamated epithelial cells, and a granular 

 debris representing the coagulated serous exudate. 



