Ofi Respiratio7i 189 



has been said, that, in trifling wounds of the chesty 

 the lungs are yet observed to move somewhat. For 

 although the air rushes into the thorax through the 

 aperture of the wound, so that the lungs are externally 

 compressed by it, still air, in quantity sufficient to fill 

 the dilated chest, cannot enter immediately on 

 account of the smallness of the wound, and therefore 

 air to fill the chest must rush in partly through the 

 wound and partly through the trachea. Hence the 

 lungs only partially expand, in the space, namely, of 

 the enlarged thorax, as yet unoccupied by the air 

 entering through the wound. But when the chest 

 contracts, most of the air which has entered through 

 the wound is expelled through the aperture of the 

 wound, since its volume is too great to be retained in 

 the now diminished cavity. When the chest, how- 

 ever, once more dilates, the air, as before, rushes not 

 only through the wound but also by the trachea, into 

 the lungs and dilates them (although with greater 

 difficulty on account of the mass it has to raise), and 

 in this way some motion' of the lungs is kept up in 

 the wounded chest. 



Here, by the way, surgeons should be warned not 

 to close the v^ound if the chest has been perforated 

 except when the thorax is contracted to the utmost ; 

 for, otherwise, if the opening made by the wound is 

 closed when the chest is dilated (that is, when the air 

 has filled the interior cavity of the thorax), it will be 

 impossible for the chest to contract on account of the 

 resistance of the air inside, or for the lungs to expand^ 

 except partially, and, in consequence, suffocation will 

 necessarily follow. 



Now that it has been shown that the entrance of 

 air into the lungs depends upon the dilatation of the 

 chest, it remains for investigation how the chest is 



