CIRRHOSIS OF THE LUNGS 57 



CIRRHOSIS OF THE LUNGS. 



Chronic Interstitial Pneumonia. 



Definition. A chronic inflammatory condition of the lungs 

 characterized by an increase in the interstitial tissue and 

 fibroid collections in the alveoli. 



Etiology. (a) Inhalation of particles of dust when con- 

 tinued for a long period produces h'brosis of the lungs, due 

 to the chronic irritation of the foreign material in the tissues. 

 The degree depends upon the amount and character of the 

 inhaled material. 



(6) Pressure upon the lungs by neighboring structures, as 

 new growths and diverticula of the esophagus, tumors in 

 the lung substance, all of which produce a reactive inflamma- 

 tion resulting in increased connective tissue proliferation. 



(c) One of the most frequent causes in small animals is 

 bronchopneumonia. When it terminates atypically fibroid 

 changes occur in some of the involved lobules. In these 

 cases the fibrosis begins as a chronic bronchitis or peri- 

 bronchitis, invading later the surrounding parenchyma of the 

 lung, which results in a great increase in the interstitial 

 tissue. This is a frequent sequel to bronchopneumonia 

 occurring during the course of infectious diseases (dis- 

 temper, etc.). For some unexplained reason resolution 

 does not occur, and the fibrinous exudate collected in the 

 alveoli during the stage of red hepatization is displaced by 

 fibrous tissue. The connective tissue formation necessarily 

 begins in the alveolar walls, as from this source must be 

 derived the new vessels which appear in the intra-alveolar 

 new formations. Proliferative changes in the alveolar epi- 

 thelium may for a time be active during this transformation 

 of the exudate, but eventually the new tissue within the 

 alveoli merges with the thickened, enclosing walls, which 

 take a relatively inactive part in the process, and the area 

 becomes entirely fibroid. Usually this lesion is only in parts 

 of the lobules, but in some cases may extend into a consider- 

 able portion of the lung tissue, involving the interstitial 

 connective tissue which is greatly increased in amount. 



(d) Localized areas of interstitial pneumonia may originate 



