116 



§ 114. The lobes of the lungs consist of an infi- 

 nite number of au'-cells, Avhich communicate with 

 the air by a multitude of tubes ; these unite and 

 reunite, until they are reduced to one on each 

 side, coming off about the centre of the surfaces of 

 contact of the lobes of that side, and these two 

 again unite into one principal tube, the " wind- 

 pipe." This sole conduit for air into the lungs can 

 easily be felt as it passes upward above the breast- 

 bone. 



§ 115. In front of the neck vertebrae the wind- 

 pipe is surmounted at top by a sort of box, of 

 considerable size, called the " laeynx," prominent 

 in front as " Adam's apple." To this box there is 

 but a single small opening, through the membrane 

 which forms its upper part, and this opening can, 

 at any time, he dosed by a lid called tlie " epiglot- 

 tis." 



It is evident that the amount of air surface 

 which can come into action against the smaU un- 

 der surface of this Hd is exceedingly limited, com- 

 pared with the surface presented by the air in the 

 lungs, and that thus the slender muscles, which 

 close the Hd, are quite competent to hold it tight 

 against any escape of that fluid, even when the 

 most violent compression of the hmgs, from the 



