106 DR. R. ANGUS SMITH PHYSIOLOGICAL EFFECTS OF 



mical solution_, it would be still more the case. If we add 

 oxygen to protocarbonate of iron in water_, tbe carbonic 

 acid is driven out in proportion to the rapidity with which 

 the oxygen is absorbed^ and of course the oxygen is ab- 

 sorbed with greater rapidity if the liquid contains less car- 

 bonic acid. 



If, again^ we view the blood and the membranes rather 

 as porous bodies^ we have the question still more clearly 

 answered ; and there are reasons why we should believe the 

 action somewhat to resemble the action of these bodies. 

 Whenever charcoal^ a porous body^ is filled with one gas 

 and is put into another^ a certain amount of the first is 

 driven out with great force ; the result is not a mere 

 mixture taking place quietly, but an instant forcible dif- 

 fusive and absorbent action. If we view the carbonic acid 

 as driven out by the oxygen, taking any of the three views, 

 the actual amount of the gases present must be of the 

 greatest importance. 



The amount of carbonic acid in the lungs is always 

 considerable. If the air inspired has more or less oxygen, 

 the proportions are first changed in the lungs, then the 

 act of absorption takes place, when the proportions must 

 again be changed. We must remember that we breathe 

 every three seconds, so that the change in the lungs is 

 made rapidly; and the absorption will also be rapid, although 

 the chemical changes taking place in the blood may be 

 slower. 



I must be careful in speaking of such subjects; but I 

 trust I do not go farther than is legitimate for a chemist. 



If we consider the effect of even one beat of the heart in 

 a minute in a mechanical point of view, we need not be 

 surprised at a change of result in the health. If the 

 amount of blood sent by the heart is three ounces, we 

 have, for every beat of the pulse lost per minute, a dimin- 

 ished circulation of many gallons of blood per day; for 



