INFLAMMATION OF THE PLEURA: PLEURISY. 131 



are present in quantities, the purulent or suppurating form is seen. 

 True purulent exudation is always caused by the presence of a 

 specific purulent poison, and becomes fetid as soon as decayed or 

 gangrenous agents find their way into the pleural cavity, as in gan- 

 grene of the lungs, perforation of the throat by foreign bodies, in 

 deep wounds of the chest, and in perforation of the oesophagus in 

 the thoracic cavity. 



The excretion which collects rapidly crowds the lung of the 

 aflfected side and finally presses it against the spinal column and 

 mediastinum, pressing the lung into an inert mass. The opposite 

 lung is the seat of considerable collateral hypersemia, which may 

 lead to oedema, according to the severity of the condition. When 

 compression of a lung is continued for any length of time the 

 alveoli lose entirely their functional activity, their walls collapse 

 and become adherent if the fluid exudated finally becomes absorbed. 

 After this has occurred it can readily be recognized by the depressed 

 appearance of the ribs. In cases of primary pleuritis which were 

 seen by the author the inflammatory process was always restricted 

 to one side, and that, as a rule, was the left side. The cases of 

 secondary pleuritis were generally double-sided, but the inflamma- 

 tory conditions are never of equal intensity on both sides, one side 

 being always a little worse than the other. Besides having the 

 results of pressure shown on the lungs, we also have the heart 

 pushed toward the healthy side of the mediastinum or the dia- 

 phragm. 



The conclusion of pleuritic inflammation depends on the inten- 

 sity and duration of the disease and the character of the exudate. 

 In favorable cases the latter is reabsorbed and good results follow. 

 In serious cases only part of the liquid portion of the exudate is 

 absorbed, while a fibrinous exudate covers the pleura; this becomes 

 converted into a granular tissue, containing numerous vessels, and 

 later into a stringy cicatricial tissue, called a pleuritic sward, and 

 more or less adhesions of the pleura between the lungs and inner 

 wall of the thorax and between the lungs and diaphragm. 

 Although the sward formations may be very extensive, it is pos- 

 sible for the lung to regain its normal extension, but it takes a long 

 time. Thin adhesions sometimes tear; extended adhesions offer a 

 constant hindrance to the unrestricted use of the affected part of 

 the lung. Purulent exudates are sometimes reabsorbed; but, as 



