PHYSICAL anv LITERARY. 305 
along the pleura, and though this mem~ 
brane is in different ftates: While the crea- 
‘ture infpires, it is concave; during ex{pi- 
ration it is convex and prominent out- 
wards, 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 condenfation and expanifili- 
ty in the lungs than the external air has. 
Ir we were to find accurately what 
weight the pleura could raife when it is 
made convex during ex{piration in the pre- 
ceeding experiment, would not this de- 
‘termine how much more preffure, than 
that of the atmofphere, the part of the 
lungs within this elevated p/eura, on which 
this weight is fuftained, is expofed to? 
WOULD not the preflure on the fame 
part of the lungs, during infpiration, be 
early as much lefs than the weight of 
on as is the weight raifed in 
exfpiration ; fince it is the fame glottis 
Vor. IL Qq which 
