ON THE ANIMAL FRAME. 297 



become filled with that element, a proof that the 

 body is lighter than water. And many persons 

 are observed to swim with the whole head con- 

 stantly above the surface of the water. 



Have we overrated the specific gravities of the 

 component parts of the body? I think not: 

 bpnes, and flesh, and blood are certainly all hea- 

 vier than water, some more some less. 



Has the capacity of the lungs for air been 

 underrated ? I cannot imagine that any one will 

 contend that the lungs of a middle sized man 

 will hold at a medium state of inflation six times 

 the volume of air we have assigned. 



Upon the whole I am inclined to believe tlie; 

 true explanation of the difficulty will be found 

 in this, that the whole substance of the body 

 is pervious to air, and that a considerable portion 

 of it constantly exists in the body during life, 

 subject to increase and diminution according to 

 the pressure of the atmosphere, in the same 

 manner as it exists in water: and further, that 

 when life is extinct, this air in some degree 

 escapes and renders the parts specifically heavier 

 than when the vital functions were m a state of 

 activity. 



2 p 



