278 ESSAYS AND OBSERVATIONS 



during exfpiration it is convex and prominent 

 outwards, for this plain reafon, that while in- 

 fpiration is performing, the air does not pafs fo 

 quickly at the narrow glottis as to fill the lungs 

 at once with air of denfity and weight equal 

 to the atmofphere ; and during exfpiration, 

 the air cannot efcape fo faft at the glottis as 

 to prevent its more than ordinary condenfa- 

 tion and expanfility in the lungs than the ex- 

 ternal air has. 



If we were to find accurately what 

 weight the pleura could raife when it is 

 made convex during exfpiration in the pre- 

 ceeding experiment ; would not this deter J 

 mine how much more prefTure, than that of 

 the atmofphere, the part of the lungs within 

 this elevated pleura., on which this weight 

 is fuftained, is expo fed to ? 



Would not the preiTure on the fame part 

 of the lungs during infpiration be nearly 

 as much lefs than the weight of the at- 

 mofphere, as is the weight raifed in exfpi- 

 ration J lince it is the fame glottis which 

 allows the air to pafs in both cafes r 



Is not the force, by which the infplratory 

 organs, ading with the greateft energy of 

 the mind, exceed the power of the exfpira- 



tory 



