CHAPTER II 



AIE 



It is scarcely necessary to dwell upon the paramount im- 

 portance of pure air, we have only to remember that air is 

 an urgent and regular necessity ; food and water can be 

 done without for hours, even a few days, but a few seconds' 

 deprivation of air brings about an alarming change in the 

 organism. Nor is this difficult to understand when we 

 remember that the process of building up and destruction 

 in the body is constantly occurring, and that nothing must 

 interfere, even for a few seconds, with the supply of oxygen 

 and the removal of carbonic acid. 



There is no difficulty in understanding why it is that the 

 supply of pure air to the bodj' is so necessary, when we 

 consider the profound changes occurring in the blood as 

 the result of respiration. The blood must be supplied with 

 oxygen and its carbonic acid removed ; for this purpose the 

 inspired air is brought so intimately in contact with the 

 blood of the body, that only a membrane of extreme thin- 

 ness and delicacy separates the two. Nothing can be easier 

 than a conception of the influence on the blood, when 

 instead of being brought in contact with a pure atmosphere, 

 it has to effect its important chemical changes with an 

 already vitiated mixture of gases. 



Composition of Air. — Air is a mechanical mixture of three 



gases, viz., nitrogen, oxygen, and carbonic acid, with traces 



of ozone, ammonia, organic matter, mineral salts, and a 



variable proportion of watery vapour depending on the 



temperature. 



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