CARBONIC ACID AND VENTILATION. 105 



lowering of the pulse_, even in mucli less impure air, must 

 have a gradual effect on the vitality ; which effect wiU be 

 seen in some persons in a few hours, in some after days, 

 and in others perhaps years. It is probable that to live 

 during the whole 24 hours of the day in any air containing 

 above i per cent, would bring results on the health very 

 rapidly ; but no men are exposed to this, so far as I know ; 

 the usual exposure is only for three or four hours, seldom 

 during the whole working time ; and even with this the 

 pulse is kept permanently low, as will be seen in Dr. Pea- 

 cock^s report. 



Now comes the question. If the oxygen of the air is 

 taken up by the blood by chemical afl&nity, why should 

 the presence of carbonic acid affect it, and therefore why 

 should it be a matter of importance whether the amount 

 of oxygen be small or great ? 



1st. The absorption cannot be wholly chemical ; it must, 

 to some extent, follow the physical laws of absorption, if we 

 may so call them. In this case the amount absorbed will 

 be in proportion to the bulk of the two gases presented to 

 the liquid. The smallest increase of either gas will make 

 a difference. I entered on this more fully in a former 

 paper. 



2nd. If the absorption is purely chemical, knowing as 

 we do that the work of absorption must be done rapidly, 

 the amount absorbed must stiU depend on the amount 

 presented. 



3rd. In either case it will require a certain amount of 

 oxygen to drive out the carbonic acid. 



If blood contains 10 per cent, of oxygen and 5 of car- 

 bonic acid, add one per cent., or one-tenth, or one-hundredth 

 per cent, of oxygen more, and a certain amount of carbonic 

 acid will bo removed. 



Viewing blood as a liquid like water, this would be the 

 case, I suppose, if we gave it time. Viewing it as a che- 



