THE RESPIRATORY SYSTEM. 473 



Suppurative Pleurisy (Empyema). Suppurative pleurisy may occur 

 either with or without the formation of a considerable sero-fibriuous exu- 

 date. The exudate may be purulent from the beginning, or a sero-fibrin- 

 ous exudate may assume this character. 



The pleural cavity in empyema is partly or completely filled with 

 purulent fluid, and the lung is either compressed against the vertebral 

 column or partly adherent to the chest wall. Sometimes, however, the 

 purulent fluid is shut in by adhesions, either between parts of the lung 

 and the thoracic wall, or between the lung and the diaphragm, or between 

 the lung and the pericardium, or between the lobes of the lung. 



The fluid in the pleural cavity is usually a thin, purulent serum, 

 composed of serum, pus cells, mesothelial cells, and flocculi of fibrin ; 

 but sometimes this fluid is thick and viscid. 



While in children the more or less active Suppurative process in the 

 pleura may continue for a long time without deep involvement of the 

 pleura, in adults granulation tissue may form upon the pleura, which 

 thus becomes gradually thickened and may so remain for mouths with 

 its inner vascular surface covered with pus and fibrin. In such cases as 

 well as in less chronic forms the fibrin fibrils are often swollen and coa- 

 lesce to form irregular homogeneous or finely granular masses. Resolu- 

 tion may occur in one region of the pleura while the exudate in another 

 may become encapsulated by new-formed connective tissue. 



In old cases the thickening of the pleura may be great and it may 

 become calcified. 1 The perichondriuni of the cartilages and the peri- 

 osteum of the ribs may become inflamed, with necrosis of the cartilages 

 and ribs or a production of new bone. Necrosis and gangrene of the 

 involved pleura may occur and putrefactive process be set up in the exu- 

 date. The Suppurative process may extend from the pleura involving 

 adjacent parts, such as the fasciae, the muscles, the skin, the diaphragm, 

 or the lungs. Thus the pus may find an exit, through the wall of the 

 thorax, into the peritoneal cavity or into the lungs. 



In inflammation of the pleura the process may extend to the lymphat- 

 ics in the interlobular septa, around the bronchi, and around the blood- 

 vessels. This interlobular lymphangitis occurs more frequently in chil- 

 dren than in adults. The lymphatics in the interlobular septa and those 

 around the bronchi and blood-vessels are distended with pus cells, the 

 septa are much thickened, and the lobules separated from each other. 



Sero-fibrinous pleurisy and empyema may occur as complications of 

 infectious diseases, such as scarlatina, typhoid fever, and various forms 

 of septicaemia, or by an extension of an inflammatory process from such 

 adjacent parts as the pericardium, lungs, mediastinum, etc. 8 The vari- 

 ous forms of pneumonia are frequently associated with local or general 

 inflammation of the pleura. 



1 For a resume of our knowledge of various calcifications in the lungs, and allied 

 conditions often called "lung stones," consult Polaillon, "LesPierres du Poumon,"etc., 

 Paris, 1891; or Legry, Arch. gen. de Med , March and April, pp. 5537 and 466, 1892. 



' 2 For study of relation of cesophageal diverticula to empyema see Starck, Arch. f. 

 Verdauungskr., Bd. vii., 1901, p. 1 



