STRUCTURE OF THE LUNGS. 187 



process which, because of its intimate relation to the cir- 

 culation, may be considered here, rather than with the 

 other excretory functions. 



Position and Structure of the Lungs. 



The lungs occupy the greater portion of the chest, or 

 uppermost of the two cavities into which the body i& 

 divided by the diaphragm (fig. 31). They are of a spongy 

 elastic texture, and on section appear to the naked eye a& 

 if they were in great part solid organs, except here and 

 there, at certain points, where branches of the bronchi or 

 air- tubes may have been cut across, and show, on their 

 surface of the section, their tubular structure. 



In fact, however, the lungs are hollow organs, and we 

 may consider them as really two bags containing air, each 

 of which communicates by a separate orifice with a common 

 air-tube (fig. 31), through the upper portion of which, 

 the larynx, they freely communicate with the external 



Fig. 56*. 



atmosphere. The orifice of the larynx is guarded by 

 muscles, and can be opened or closed at will. 



* Fig. 56. Transverse section of the chest (after Gray). 



