THE RESPIRATORY SYSTEM. 475 



blood. The exudate may be purulent. The tubercle bacillus may be 

 associated with other bacteria, most often with the Staphylococcus pyo- 

 genes in the purulent exudate. 



Many cases of pleuritis with a sero-fibrinous exudate giving no growth 

 of bacteria on the ordinary culture media are found to be tuberculous, by 

 the inoculation of guinea-pigs with the fluid. 



TUMORS. 



Fibroma, sarcoma, and endothelioma may occur as primary tumors of 

 the pleura. Fibroma and lipoma formed in the subpleural tissues may 

 encroach upon the pleural cavity. Endothelionm usually occurs in the 

 form of larger and smaller, flat or projecting, irregular nodular masses 



FIG. 260. -EXDOTHEUOMA OF THE PLECRA. 



The inner surface of a segment of the costal pleura, containing three of the ribs, is shown in the cut. 



(Fig. 260), frequently most marked and extensive upon the costal 

 pleura (Figs. 300 and 301).' This as well as other tumors of the pleura 

 may be associated with an exudative pleuritis. 



Carcinoma, primary in the thyroid, mamma, resophagus, and stomach, 

 may invade the pleura. Small white, slightly projecting, often pig- 

 mented elevations of the pleura, either single or multiple, are com- 

 mon. These were formerly regarded as mostly miliary fibromata. But 

 Hodenpyl and others have shown that while some may be fibromata or 

 lymphangiomata or air cysts, they are mostly fibrous masses which replace 

 or enclose miliary tubercles. Echinococcus and other cysts of the pleura 

 have been recorded. 2 



1 For bibliography of endothelioma of the pleura consult Glockner. Zeits. f. Heil- 

 kunde, Bd. xviii., p. 209, 1897. 



- For a description of ciliated cysts of the pleura see Zahn, Virchow's Arch., Bd. 

 cxliii., p. 171. 



