14 THE LAWS OF OK CAN 1C 



vast quantity of blood to circulate at the same 

 moment in them ; and the same adaptation fa- 

 vours, in like manner, the more general dif- 

 fusion of the air ; so that, in the usual operation 

 of the pulmonic functions we may conclude 

 that about 300 cubic inches of air are acting 

 simultaneously upon this fluid ; and, still fur- 

 ther, that the expiration of 40 cubic inches is 

 the whole of that portion which is rendered unfit 

 for the purposes of life by the action of the blood. 

 It is impossible to suppose, that air is deteriorated 

 immediately on its being inspired ; if this were 

 allowed, the whole quantity which belongs to 

 the lungs would be unfit for its vital function, 

 as this must be contained in the air-cells and 

 subject to the influence of the capillary vessels, 

 and therefore placed under circumstances that 

 would deprive it of its properties. 



XXI. This contrivance is a wise provision of 

 Nature, as it enables an individual to speak, 

 laugh, run, in fine, to accommodate himself to 

 any kind of exercise where expiratory actions 

 are required, without immediately affecting the 

 office of the lungs, which would necessarily be 

 implicated if the inspired air were instantane- 

 ously appropriated to those changes which are 

 indispensable for the continuance of life. 



The short breathing which an individual ex- 

 hibits after violent exercise, as after running, is 



