CHAPTER V. 

 DISEASES OF THE PLEURA. 



PLEURITIS. 



Definition. — ^An inflammation of the plem-a. Plem-itis is 

 nearly always a secondary condition in animals. 



Prom a pathological standpoint pleuritis may be classi- 

 fied into: Serofibrinous, fibrinous, purulent (empyema of 

 thorax), ichoric (putrid) and hemorrhagic. Clinically these 

 differentiations are difficult to make. Fibrinous pleuritis 

 ("dry pleurisy") is rarely diagnosed intra vitam. By punc- 

 tiu-ing the thorax with a trocar the character of the exudate 

 may be determined, i. e., whether serous fluid with flocculse 

 admixed, pus, ichor, etc. The most common form of pleuritis 

 is the seroflbrinous here described. 



Occurrence. — ^Affects all animals but principally the horse. 

 In the horse pleuritis is usually a symptom of infectious 

 fibrinous pneumonia; in the ox of tuberculosis, contagious 

 pleuropneumonia and hemorrhagic septicemia, and in swine 

 most frequently of so-called swine plague. Pleuritis, how- 

 ever, may occur unattended by pneumonia as is frequently 

 observed in horses. 



Etiology. — ^Pleuritis in animals is always due to infection. 

 Cold, which was believed to be the most potent etiological 

 factor, is now considered merely predisposing' (pleuritis in 

 sheep following shearing; exposure of horses to cold wind 

 and rain). The microorganisms which produce pleuritis are 

 many. Rarely is pleuritis a primary disease — it is most 

 commonly seen in practice accompanying diseases of the 

 lungs (pleuropneumonia). The microorganisms causing 

 pleuritis may enter as follows : (a) Through penetrating 

 thoracic wounds; (6) through deep contusions on the chest 

 wall, especially if rib fractures be present (kicks, blows, 



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