162 Inllaiiiiiiatioii (.f the Pleui'a. 



rule, however, bacteria do not invade the pleura under these 

 circumstances, but the injured tissues may produce an inflam- 

 mation by chemotactic action, which is limited to the injured 

 territory. All these traumatic insults may cause injuries to 

 the lungs and may cause the invasion of bacteria from the in- 

 haled air into the pleural cavity. More dangerous are internal 

 injuries produced by fragments of lione or other bodies which 

 penetrate from the esophagus or stomach into the thoracic 

 cavity. 



In the great majority of cases pleuritis develops in con- 

 nection with an inflanmiation of the immediately adjoining* or- 

 gans, especially the lungs, in such a manner that the bacteria 

 causing pneumonia get to the surface of the pleura with 

 the lymph current or else the inflammation spreads by 

 continuity. Pleuritis very frequently follows upon croup- 

 ous pneumonia, more rarely catarrhal pneumonia; but in 

 some epizootics almost every case of bronchopneumonia 

 leads to pleuritis. Equine influenza is accompanied in 

 almost every case by an intense pleuritis. In purulent pneu- 

 monia and gangrene of the lungs pleuritis may occur even with- 

 out any breaking through of the pulmonary abscess or danger- 

 ous focus. Tuberculosis and pulmonary glanders, also bron- 

 chial catarrh, may furnish the starting point for pleuritis. 



Diseases of the other neighboring organs more rarely lead 

 to a secondary pleuritis. Among them are to be mentioned 

 purulent mediastinitis in the course of strangles, rupture of 

 an esophageal diverticulum or perforation of the thoracic por- 

 tion of the esophagus by a foreign body, acute and frequent 

 traumatic pericarditis, which occurs particularly in cattle, car- 

 ies and necrosis of neighboring bones, especially the ribs and 

 sternum, acute inflammation of the peritoneum and of the ab- 

 dominal organs. 



In the course of acute general infectious diseases pleuritis 

 likewise is not uncommon. In this respect the diseases ought 

 to be first mentioned which are caused by the bipolar bacilli 

 (see Vol. I) which may cause pleuritis without a pneumonia ex- 

 isting simultaneously. In the course of pyemia, in rheumatic 

 affections of the joints and of the other serous membranes, in 

 variola and so forth, pleuritis occasionally makes its appear- 

 ance. 



Pleuritis is caused exceptionally by chemicals (bacterio- 

 toxins, constituents of urine retained in the blood in nephritis) ; 

 mechanical irritation (tumors of the pleura or neighboring or- 

 gans) in very rare cases by tapeworm, pleurocercoides Baillet 

 (Lefebre and Guerin), Cysticercus tenuicollis. 



Cold frequently plays a certain role, aside from the causes 

 mentioned ; its influence may be very obvious, so that it is easy 

 to understand why cold was formerly considered the exclusive 

 cause of primary pleuritis. The majority of authors (Fried- 

 berger & Frohner, Kitt) believe even to-day in the occurrence 



