WOUNDS OF THE CHEST. 113 



tissue is found underneath the skin, between the muscles and other 

 structures near the surface of the body. This is generally first 

 noticed near the wound, but may extend, more or less, over the 

 body, which will have a blown-out appearance. As a rule it occurs 

 by air, during inspiration, entering the pleural sac either through 

 an external wound or a wound in the lung ; and, failing to obtain 

 exit by means of its way of entrance, being squeezed by the elastic 

 recoil of the ribs during expiration, into the loose connective tissue 

 which lies open on the wounded surface of the chest wall. In cases 

 of emphysema, the return of the air is prevented by the valve-like 

 action of the wound, or wounds. Emphysema requires little or no 

 special treatment, as it is seldom hurtful. If, as might happen in 

 very rare cases, it interferes with the breathing, let out the air 

 through the skin, at convenient spots, with the knife, or trocar 

 and cannula. 



(3.) Pneumothorax or accumulation of air in the pleural sac 

 either from an external opening or from a wound in the lung. 

 This condition is brought on in the same manner as emphysema, 

 and it is dangerous, owing to its liability to cause '" collapse of the 

 lung." As the act of inspiration is that of enlargement of the 

 cavity of the chest, which in health reduces the air pressure in the 

 lung and thus causes the lung to "become inflated by the in-coming 

 air ; the presence of air in the pleural sac will, by the resulting 

 pressure on the surface of the lung, directly oppose the perform- 

 ance of this function, and will accordingly give rise to more or less 

 difficulty of breathing. To relieve this serious condition, enlarge 

 the external wound, if th'ere be one ; or tap the distended pleural 

 sac with a trocar and cannula, which is an operation that demands 

 an accurate knowledge of the anatomy of the part. The chest may 

 be largely opened and yet no collapse take place. This seems most 

 probably to be due to the adhesion of the two smooth moist pleural 

 surfaces to each other. When a fair-sized external opening com- 

 municates with a wound in the lung, air will rush in through the 

 external opening during inspiration, and be more or less expelled 

 out through it during expiration. 



(4.) Pleurisy and (5) pneumonia will respectively follow wounds 

 of the pleura and lung. Little can be done to relieve these compli- 

 cations beyond carefully nursing the patient. 



(6.) Empyema, or pus in the pleural sac, is a very serious con- 

 dition usually brought on by contamination of blood or of in- 

 flammatory discharges which have accumulated in the pleural sac, 

 or by the entrance into it of dirt and other germ-laden material. 

 Treatment should consist of a thorough disinfection of the part by 

 an antiseptic solution (p. 67) and effective drainage, by, if neces- 

 sary, enlarging the external wound, and making a counter-opening 



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