THE RESPIRATORY TRACT. 717 



tant condition of different diseases which terminate fatally. In 

 microscopical examination of specimens of lungs hardened in a 

 solution of chromic acid, oedema can be diagnosticated by an 

 engorgement of the capillaries with blood, by a slight enlarge- 

 ment of the interstitial connective tissue, due to the saturation 

 with a serous liquid, without marked inflammatory changes, and 

 by the presence of a finely granular mass, the coagulated sero- 

 albuminous liquid within the alveoli. In this mass are imbedded 

 a comparatively small number of red blood-corpuscles of bio- 

 plasson bodies, which are probably emigrated colorless blood- 



FIG. 319. ALVEOLI OF THE LUNG OF MAN. BLOOD-VESSELS 

 INJECTED. 



A, alveolus ; V, pulmonary vein, sprung from the union of the capillary reticulum; W, 

 wall of the alveolus ; E, flat epithelia, covering the inner surface of the alveolus. Magnified 

 500 diameters. 



corpuscles, and detached epithelia of the alveoli, which are 

 swollen and partially dropsical. 



Pigmentation of the lungs is never found in newly born 

 children, but is marked in proportion to the exposure of the indi- 

 vidual during life to a smoky or dusty atmosphere. The lungs of 

 tobacco-smokers and coal-workers show high degrees of black 

 pigmentation, which gives the tissue a peculiar variegated 

 appearance. The lungs of laborers in coal-mines, in iron foun- 



