316 
that this attraction and condensation of gases is not 
effected by pulverized charcoal, just as M. de Saus- 
sure found the attractive power of leaves to be de- 
stroyed (342.) when they were beaten to a pulp. 
614. If, then, it appear, from the foregoing facts, 
that air adheres to the surfaces of all bodies ; that ani- 
mal substances possess'a strong attraction for gaseous 
fluids ; and that the air, received into the lungs, is 
spread over a surface ten times greater than that of 
the whole body ; may we not reasonably presume^ 
that such an attractive force, operating to so great 
an extent, may constrain the elasticity of the inspired 
air, and, like the porous structure of charcoal, con- 
siderably reduce its volume ? If such or any simi- 
lar cause be allowed to act, it would follow, that, al- 
though the lungs do not contain a greater bulk of 
air than has been commonly supposed, yet that, in 
fact, they contain a greater weight of that elastic 
fluid ; and hence, when any portion of this air is 
expelled, it will occupy a greater space than before, 
by escaping from the constraint to which it was pre- 
viously subjected. This attractive force between the 
air and the animal substance, may, also, be exerted 
by different gases ; and hence, as in the foregoing 
experiments of Allen and Pepys, oxygen, nitrogen, 
and hydrogen gases may be successively attracted 
and retained in nearly equal proportions, and thereby, 
in turn, produce each other's expulsion. 
615. This supposed reduction of the elasticity of 
the air in the lungs does not stand in opposition 
either to anatomical or chemical principles ; for it is 
considered to take place only at the surface of the 
