248 Vcteri)iary Medicine. 



granules, little knobs and threads between and on the endothelial 

 cells and entangling a few pus cells. The changes are now much 

 more marked in the connective tissue cells, which are more 

 numerous, larger, nucleated and often stellate or polygonal. 

 Changes are well advanced in twenty-four hours. The cells 

 go on increasing to the fourth or fifth da}^ when new blood vessels 

 are formed into the membrane and may be injected from the 

 pleura. From this time, in favorable cases absorption of the 

 liquid proceeds, and the fibrine is organized, and by the fourteenth 

 day is transformed into connective tissue, the superficial cells 

 forming endothelium and the deeper, branching connective tissue 

 cells. The result is the thickening of the pleura and the forma- 

 tion of adhesions. The case, however, may prove fatal, or it may 

 be protracted through the continued production of fibrine and 

 serum, or it may pass into empyema. 



3. Sero-fibrino-purulent pleurisy. Empyema. This is 

 usuall}^ very dangerous as well as complicated. It may supervene 

 on the last described form. It may depend on rupture into the 

 pleura of abscess of the lung, bronchial glands, liver, diaphragm 

 or intercostal space and the infection of the chest cavity. It may 

 in the same way follow the laceration of a bronchium by a broken 

 rib, the perforation of the intercostal space by a foreign body, or 

 (in cattle) the penetration of the chest by a sharp-pointed body 

 from the recticulum. It may follow at once on pleurisy of a very 

 high grade. Probably in all such cases there is infection of the 

 pleura by pus microbes. When there is a communication with a 

 bronchium, the reticulum or the external air there are usually 

 septic germs in addition, and the contents of the chest become 

 foetid. 



The purulent fluid may accumulate in the lower part of the 

 pleural sac, or it may be confined in abscess form in the false 

 membrane, and extend thence into surrounding tissues. The pus- 

 containing pleura, or cavity infected by the pus germs, assumes 

 the appearance of a granulating surface, or of the lining mem- 

 brane of an abscess, and continues to produce pus in greater or 

 less amount. 



The formation of pus in the pleura is known as empyema. 

 When air enters the pleura through a wound perforating the chest 

 wall, or when gas is formed in the pleura, the condition is pneu- 



