THE RESPIRATORY SYSTEM. 



487 



As already indicated, emphysema of the lungs is often associated with 

 chronic bronchitis. With this may be more or less hyperplasia of the 

 interstitial tissue. Dilatation or 

 hypertrophy of the wall of the 

 right ventricle is common. 

 Chronic endarteritis of the pul- 

 monary vessels may be associated 

 with emphysema. There may 

 be chronic venous congestion of 

 the abdominal viscera and 

 dropsy. Delafield holds that 

 the more essential lesion in some 

 forms of emphysema is the de- 

 velopment of new connective tis- 

 sue with which dilatation of the 

 air vesicles and atrophy of their 

 walls are in varying degrees as- 

 sociated. 



In old age, atrophic processes 

 in the lungs may be associated 

 with dilatation and mergence of 

 the air spaces. This is called 

 senile emphysema. Excessive 

 emphysema, apparently congeni- 

 tal, may be present in young 

 children (see Fig. 269). 



Interstitial Emphysema. 

 Eupture of the walls of the air 

 spaces may permit the escape of 

 air into the interstitial tissue of 

 the lungs. Kupture of the pul- 

 monary pleura may admit air 

 into the mediastinum and thence FIG. 269.-i NT ERLOBUL A R EMPHYSEMA OF LUNG. 



into the tissues Of the neck. Gas Child two months old. After whooping-cough. 1 



may form after death in the in- 

 terstitial tissue of the lungs from the presence of the Bacillus aerogenes 

 capsulatus or other putrefactive bacteria. 



GANGRENE. 



Circumscribed gangrene occurs in the form of one or more rounded 

 or irregular masses of variable size. The gangrenous portion of lung is 

 at first brown and dry. The surrounding lung tissue is congested or 

 oadematous, or infiltrated with blood, or inflamed. If the gangrenous 

 focus is near the pleura, the latter will be coated with fibrin. Gradually 



' For a fuller description of this unusual case see Northrup, Am. Jour. Med. Sci., 

 vol. Ixxxvi., 1883, p. 147. 



