MECHANISM OF RESPIRATORY ACTIONS. 231 



Mechanism of Various Respiratory Actions. 

 It will be well here, perhaps, to explain some respiratory 

 acts, which appear at first sight somewhat complicated, 

 but cease to be so when the mechanism by which they 

 are performed Fig. 65. 



is clearly un- 

 derstood. The 

 accompanying 

 diagram (fig. 

 65) shows that 

 the cavity of 

 the chest is 

 separated from 

 that of the 

 abdomen by 

 the diaphragm, 

 which, when 

 acting, will les- 

 sen its curve, 

 and thus des- 

 cending, will 

 push downwards 

 and forwards 

 the abdominal 

 viscera; while 

 the abdominal 

 muscles have 

 the opposite 

 effect, and in 

 acting will push the viscera upwards and backwards, and 

 with them the diaphragm, supposing its ascent to be not 

 from any cause interfered with. From the same diagram 

 it will be seen that the lungs communicate with the 

 exterior of the body through the glottis, and further on 

 through the mouth and nostrils through either of them 



