SECTION IV. 

 DISEASES OF THE PLEURA. 



OHAPTEK I. 



INFLAMMATION OF THE PLEURA PLEURITIS, PLEURISY. 



ETIOLOGY. As we shall find presently, there are two forms of pleu- 

 risy. The first form merely causes thickening of the pleura, and 

 adhesion of its opposing surfaces. The second also produces thick- 

 ening, but at the same time gives rise to an effusion into the pleural 

 sac, containing more or less of fibrin and of young cells. The thick- 

 ening and adhesion of the pleural surfaces are due to proliferation of the 

 normal connective tissue of the pleura. The pleuritic effusion is the 

 result of an interstitial exudation. The young cells, which the effusion 

 contains, owe their origin to a proliferation of the connective tissue cor- 

 puscles of the pleura, and of the epithelial cells which cover its surface. 



Regarding the essential points in the etiology of pleurisy, we may 

 refer to what has already been said with regard to the etiology of 

 pneumonia. 



We must here denounce the impropriety of calling all cases of 

 pleurisy secondary pleurisy, which, instead of attacking robust and 

 vigorous persons, occur in subjects with broken-down constitution, or 

 in individuals who have already suffered from some other disease. 

 Even the pleurisy which so often occurs in Bright's disease is not, in 

 my opinion, a secondary disease, dependent upon <he renal affection 

 but should rather be looked upon as a complication. The frequence of 

 such complications, and the especially common occurrence of pleuritis 

 in debilitated and depraved constitutions, and among convalescents 

 after protracted disease, depend upon the increased predisposition, 

 which such individuals possess, for all kinds of inflammatory diseases, 

 and especially for the one in question. A very trifling exciting cause 

 is requisite in this class of persons to provoke the malady; but it never 

 arises without provocation of some kind. 



