178 Collection of Air in the Pleural Cavity. 



tracted and variable course of the affection. Exploratory punc- 

 ture furnishes further proof; the fluid is usually only slightly 

 turbid, the specific gravity below 1016, the sediment contains 

 few white Ijlood corpuscles. Chaleur and Labasque removed 

 the transudate of a horse suffering from compression of the 

 vena cava due to a melanotic tumor, and found black, sand- 

 like masses of pigment. 



Treatment. The amelioration or aggravation of hydro- 

 thorax goes hand in hand with the primary disease toward which 

 the treatment has to be directed. If suffocation threatens, punc- 

 ture may be resorted to. It may aiford temporary relief. 



3. Collection of Air in the Pleural Cavity. Pneumothorax. 



By pneumothorax in the limited sense of the term is meant 

 a pathological condition, when atmospheric air gets between 

 the parietal and visceral layers of the pleura and causes col- 

 lapse or compression of the lungs. Those rare cases must also 

 be included where other gases get into the pleural cavity. 



Etiology. Air is enabled to enter into the pleural cavity 

 in consequence of penetrating traumatic injury to the chest 

 wall, on account of the negative pressure in the chest cavit}^ 

 The lungs then collapse in consequence of their elasticity. 

 Pneumothorax is similarly brought about when a foreign body 

 penetrates into the diaphragm from the omasum; so that the 

 gases in the latter can get into the pleural cavity. Pneumothorax 

 is also frequently observed in consequence of disease of the lungs. 

 Injury to the lungs may occur in penetrating trauma to the 

 thoracic wall, in subcutaneous fracture of the ribs, or through 

 a foreign body aspirated into the air passages. The possibility of 

 rupture of the superficial strata of the lungs also exists when 

 the air in the lungs is suddenly placed under high pressure 

 (cough, violent action of the abdominal walls, drawing of heavy 

 loads, vomiting, great efforts, continuous bellowing, falling, 

 sudden pressure upon the thorax, etc.). Purulent or ichorous 

 pulmonary foci communicating mth bronchi, occasionally echi- 

 nococcus cysts (Deupser, Sperling) may break into the pleural 

 cavity. Perforation of the pharynx may in very rare cases lead 

 to pneumothorax. 



Pathogenesis. The amount of air or gas which enters 

 depends upon the character of the opening. If the latter is not 

 closed (open pneumothorax) enough air enters to bring about 

 a degree of collapse of the lungs which is seen in cadavers after 

 opening of the thorax. Later on the air left in the lungs is also 

 absorbed and the latter may become entirely void of air. If, 

 however, the opening is of such type that it will open during 



