PATHOLOGICAL STATES OF THE LUNGS. 



581 



A continually increasing number of arborescent hollow processes 

 spring from the extremities of the original protrusions, and in the 

 6th month the air-cells are developed from the dilated extremities. 

 New cells are, however, continually added, up to birth, but not sub- 

 sequently. Before they are filled with air in the new-born child, 

 they are o f * n inch, and after breathing, 3^ to 3 <y of an inch 

 in diameter. The subsequent increase of the lungs consists in an 

 expansion of all their parts. 



Pathological States of the Lungs. 



1. In emphysema, the air-cells become permanently dilated to two 

 or three times their normal diameter; or become even ruptured, so 

 that the cells of the same, or even of different lobules, become con- 

 fluent. Their wall becomes very thin. 



The bronchial arteries become dilated in cases where the circula- 

 tion through the pulmonary arteries is interrupted ; the former re- 

 placing branches of the latter, and becoming aerating vessels. 



2. Hypertrophy of the air-cells occurs in hypertrophy of the lungs 

 from increased functional action. 



3. The air-cells become obliterated by exudation or deposit (e. g. 

 tubercular), in the cavities or their walls, or into the interlobular 

 areolar tissue. Red hepatization is produced by a complete filling 

 of the air-cells by the exudation of pneumonitis; in gray hepatiza- 

 tion the walls of the cells and the interstitial tissue become softened, 

 and undergo a fatty metamorphosis. (Kdllikerf) 



Fig. 408. 



Fig. 409. 



Fig. 408. Section of gray granulations, after addition of acetic acid ; showing the air-cells filled 

 with tubercle nuclei. 

 Fig. 409. Cretaceous transformation of tubercle, with crystals of cholesterine. 



1 See also p. 193, 2. 



