472 THE RESPIRATORY SYSTEM. 



chest. The affected portions of pleura are dull and lustreless and coated 

 with fibrin, opposing surfaces often being joined by bauds of fibrin. 

 There are swelling, degeneration, proliferation, and exfoliation of the 

 mesothelium, with swelling and proliferation of the connective-tissue 

 cells beneath. Exceptionally, there is involvement of the entire pleura 

 of one side, with the production of such a large amount of fibrin as 

 seriously to compress the lung. ' 



Sero-Fibrinous Pleurisy (Pleurisy with Effusion). This is the most com- 

 mon form of pleurisy. As a rule, it involves the greater part of the 

 pleura of one side of the chest. Sometimes, however, the pleura of both 

 sides of the chest is involved, and then the pericardium also is often 

 inflamed. 



While the inflammation is in progress the surface of the affected pleura 

 is coated with fibrin, and bauds of fibrin stretch between the parietal and 

 pulmonary pleura. In the pleural cavity is serum in variable quantity. 

 This serum is clear, or turbid from the presence of exfoliated mesothe- 

 lium, leucocytes, and flocculi of fibrin or red blood cells. The lung is 

 compressed in different degrees and positions, according to the quantity 

 of the serum and the character of the adhesions. The heart may also be 

 displaced by the accumulated exudate. 



The natural termination of such a pleurisy is the recovery of the 

 patient, with thickenings of the pleura and adhesions. The irregular 

 terminations are : The death of the patient, the protracted existence of 

 the fibrin and serum, and the change of the character of the inflamma- 

 tion so that pus is produced. 



If the patient recover, the serum is absorbed, the fibrin disappears, 

 and repair is effected, as in simple fibriuous pleurisy, by the formation 

 of granulation tissue, which gradually becomes dense and cicatricial in 

 character and may remain as local or general thickenings or firm adhe- 

 sions of the opposed pleural surfaces. The lung may be distorted by 

 contraction of the new-formed connective tissue. The exudates in the 

 sero-fibriuous form of pleurisy do not usually infiltrate the pleura, but 

 gather upon its surface and in the cavity. 



THE EXCITANTS OF SERO-FIBRINOUS PLEURISY. Cultivations from 

 the exudate give in the larger proportion of cases negative results ; but 

 the pneumococcus, Streptococcus pyogenes, Staphylococcus aureus and 

 albus, and the typhoid bacillus have been isolated. When the inflam- 

 mation of the pleura is consecutive to acute lobar pneumonia, the 

 pneumococcus may still not be found in the exudate. The presence 

 of the streptococcus is frequently followed by the formation of pus. 

 The organisms named above may be present alone or in various associa- 

 tious. Many cases with simple sero-fibriuous exudate prove on inocula- 

 tion to be tuberculous. 2 



1 For a study of the origin of fibrin and adhesions of the serous membranes consult 

 Heinz, Virch. Arch., Bd. clx., p. 365, 1900; also Gaylord, Jour Exp Med., vol. iii., p. 

 1, bibliography. 



8 For a study of the bacteria in exudative pleuritis, with the earlier bibliography, 

 consult Prudden, New York Medical Journal, June 24th, 1893 For fuller data see 

 better, Bouchard and Brissaud's "Traite de Medecine," t. vii., p 399, 1901. 



