114 INSPIRATION AND EXPIRATION. 



phragin in its descent presses upon the elastic organs of the 

 abdomen (stomach, liver, etc.), and these organs, in turn, are 

 pressed against the elastic walls of the abdomen. It is some- 

 what as if one pressed a pillow down into a rubber bag ; the 



Increased Air Space. 



Inspiration Expiration 



Fig. 45. Diagrammatic Sections of the Body in Inspiration and Expiration. 



pillow would spring up as soon as the pressure was stopped, 

 because of its own elasticity as well as that of the bag. 

 Therefore, as soon as the diaphragm relaxes, the elastic walls 

 of the abdomen retreat, and the abdominal organs rise to their 

 former place. 



When the ribs are elevated, the cartilages which connect 

 the ventral ends of the bony parts of the ribs with the breast- 

 bone are slightly bent. When the muscles relax, the elasti- 

 city of the rib cartilages helps to bring the ribs back to their 

 former position, thus reducing the chest to its former width. 



