Section V. 



DISEASES OF THE PLEURA. 



1. Inflammation of the Pleura. Pleuritis. 



Occurrence. Pleuritis is a common disease of domestic 

 animals. It usually occurs as a secondary affection, especially 

 after pneumonia, more rarely as a primary disease. In horses, 

 which are most frequently affected, pleuritis develops prefer- 

 ably after equine influenza ; in ruminants as part of the clinical 

 picture of a hemorrhagic septicema, in cattle also after pneu- 

 monia and in its chronic form on the basis of tuberculous infec- 

 tion. According to Cadeac, serofibrinous pleuritis in dogs is 

 tuberculous in nature in nine cases out of ten. The cases of 

 pleuritis which the authors have seen in dogs almost always 

 developed in consequence of tuberculosis. In fowls, pleuritis 

 is said to occur fl-equently in combination with peritonitis 

 (Guittard). 



Etiology. The true cause of a pleuritis is generally an 

 infection, while external influences only play a role as exciting 

 or predisposing causes. The disease is often found in septi- 

 cemic affections due to the bacillus bipolaris. Aside from this 

 microbe, there are frequently concerned the pyogenic bacteria, 

 the tubercle bacillus, the influenza bacterium, more rarely the 

 bacillus mallei, also, in hogs and cattle, the bacillus pyogenes ; 

 Plana saw a case of pleuritis in a dog caused by the leptothrix 

 buccalis; the authors and others saw pleuritis in dogs due to 

 streptothrix (actinomyces) canis. Eisenmann saw cases of 

 pleuritis following chronic hog erysipelas. Pleuritis fre- 

 quently follows contagious nasal catarrh of rabbits (see page 

 15). Other bacteria than those mentioned may occasionally 

 be the cause of pleuritis. 



The invasion of bacteria wdiich cause inflammation of the 

 pleura occurs in a variety of ways. After perforating wounds 

 of the thorax pyogenic bacteria usually enter the thoracic cav- 

 ity and produce a purulent pleuritis. Traumatic injuries to the 

 thorax, such as a kick, contusion, a fall upon the chest, subcu- 

 taneous fracture of the ribs, which may occur without injury 

 to the skin, give rise to the invasion of bacteria, either directly 

 from the contused spot or through the blood current. As a 



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