268 DISEASES OF THE PLEURA. 



and compression are limited to a portion of lung corresponding to its 

 seat and extent." 



The lung upon the unaffected side is always the seat of intense 

 collateral fluxion, and, in fatal cases, of collateral oedema. Should re- 

 covery take place -in this form of pleuritis, the exudation gradually 

 becomes more and more concentrated (so that the absorption proceeds 

 at first far more rapidly than it afterward does). The liquid portion 

 may at length disappear completely ; the pleural surfaces, roughened 

 by fibrinous deposit, coming into contact. The fibrin also undergoes 

 fatty metamorphosis, liquefies, and is absorbed, and then an adhesion 

 of the pleural surfaces, which are usually much thickened, always takes 

 place. Sometimes yellow, cheesy masses, consisting of remnants of 

 unabsorbed fibrinous deposit and cellular elements of the exudation, 

 are found imbedded between the adhesions. 



When absorption takes place early, the compressed lung may again 

 become pervious to the air, and may expand ; the intercostal spaces 

 may return to their normal state, and the mediastinum, diaphragm, 

 and the dislocated heart and liver, may all regain their proper places. 



In other cases the alveoli become agglutinated or adherent by con- 

 tinued pressure, or else dense fibrinous deposits upon the compressed 

 lung prevent its reinflation. The time required for the production of 

 this condition cannot be given with accuracy. If absorption of the 

 exudation should afterward take place, a vacuum tends to form, to fill 

 ap which, the thoracic wall and the adjacent organs suffer displace- 

 ment. The affected side of the chest sinks in, and may present a con- 

 cave instead of a convex surface ; the intercostal spaces become nar- 

 rower, until the ribs finally touch ; the shoulder sinks, and even the 

 spinal column becomes curved. In pleuritis of the right side, the 

 liver, previously deeply depressed, is now dislocated far in the opposite 

 direction, sometimes as high as the third rib. In pleurisy of the left 

 side, the heart, at first often displaced to beyond the right edge of the 

 sternum, now is drawn back as far as the left axillary line. 



4. Pleuritis with purulent effusion. Empyema, Pyoihorcux. The 

 liquid part of the effusion is here so rich in pus-corpuscles as to form 

 an opaque, yellow, thick fluid. The fibrinous portion also contains 

 great quantities of pus-cells and seems soft, and of a very yellow color. 

 Here too, the exudation, and not only the serous part of it, but the 

 fibrin and pus, after undergoing the often-mentioned metamorphosis, 

 may be absorbed ; but there is another sequel to pleuritis sometimes, 

 and it most frequently follows this form of the malady. Not only are 

 pus-corpuscles generated upon the free surface, but they are also 

 formed within the tissue of the pleura itself. The latter becomes 

 opaaue and softens, and irregular losses of substance occur. Should 



