180 SURGICAL APPLIED ANATOMY, [Chap. x. 



lead to surgical emphysema. The two layers of the 

 pleura are so intimately in contact with one another 

 in the normal thorax that it is difficult for the parietal 

 pleui-a to be wounded without injury to the visceral 

 layer. In wounds of the lung without external wound, 

 as when that organ is torn by a fractured rib, the air 

 escapes from the lung into the pleura, and may thence 

 pass into the subcutaneous tissues through the pleural 

 wound, thus producing both pneunio - thorax and 

 emphysema. 



It is well to note that emphysema may occur 

 about certain non-penetrating wounds of the thorax 

 when they are of a valvular nature. In such cases 

 the air is drawn into the subcutaneous tissues during 

 one respiratory movement, and is forced by another 

 into the cellular tissue, the valvular nature of the 

 wound preventing its escape externally. When the 

 pleural " cavity " is opened, the lungs become more 

 or less collapsed ; yet a few cases have been recorded 

 where the lung has protruded at the time of the acci- 

 dent through the wound in the parietes. In such in- 

 stances the glottis must have been closed, and the lung 

 fully distended at' the time of the injury ; and it must 

 be further assumed that the viscus was practically pro- 

 truded before air could enter the pleural space. It is 

 noticeable that these recent hernia3 are most common 

 at the anterior part of the chest where the lungs are 

 the most movable, and the injui'ies that bring them 

 about are often associated with violent respiratory 

 efforts at the time of the accident. In wounds of the 

 lung the blood may escape in three directions : into 

 the tissue of the organ (pulmonary apoplexy), into the 

 bronchi (causing haemoptysis), and into the pleura 

 (causing hsemothorax). In some instances the lung 

 has been ruptured without wound and without frac- 

 ture to the ribs. These cases are difficult to interpret, 

 and probably the best explanation suggested is that 



