2o POPULAR SCIENCE MONTHLY 



supplied per capita, but comparatively little effort has been made 

 to trace out and bring to light the less evident and often unsuspected 

 factors of contamination, which indicate, or at least should help to 

 determine, the logical method of relief. 



The sanitation of the air is a field which has hardly been recognized 

 as such, at least it is not carried on systematically, with that end in 

 view, and the results of present efforts, on the whole, are distinctly 

 behind the progress made in other lines. Indeed, its failure to meet 

 the aggravated needs of our crowded and growing cities can actually 

 be traced on their vital statistics. 



The Bearing of Impure Air on Health 



An exceptionally clear exposition of the process of breathing is con- 

 tained in the short essay, ' Air, and its Eelation to Vital Energy,' by 

 Professor S. H. Woodbridge, of the Massachusetts Institute of Tech- 

 nology. The oxidation of organic matter within the human body is 

 likened to the process of combustion in a boiler furnace. This analogy 

 applies to every essential point and shows that the conditions making 

 for efficiency in artificial heat production are also those which bear on 

 vital energy. The intensity of combustion within the human body 

 depends upon the rate of exchange between the carbonic acid contained 

 in the venous blood and the oxygen brought into the lungs, or the 

 rapidity at which the waste products brought in from the system are 

 being diluted. A slight abnormal accumulation of this gas in the air 

 cells of the lungs would check this outward leakage or expulsion of 

 waste products and retard regeneration of the blood, but respiration 

 automatically regulates this function. Exhausted air, with deficiency 

 in oxygen and excess of carbonic acid, to sustain equal force, thus 

 requires increased respiration, an unconscious effort, gradually lapsing 

 as the gathering waste products react upon the blood and through it 

 upon vitality. The weakened light of a candle flame in exhausted 

 room air very aptly illustrates also its effect on human beings. 



Exhausted Air. — Recent experiments by Fluegge, the eminent Ger- 

 man investigator, seemingly contradict this theory. At least they make 

 it appear that the paucity of oxygen and the simultaneous increase of 

 carbonic acid and other waste products, have no appreciable ill effect on 

 the average adult, but that the depression of spirits, headache and 

 drowsiness felt in crowded, ill-ventilated assembly rooms are principally 

 due to disturbance of the thermal functions of the body through heat 

 and moisture. Since these excesses in temperature and humidity 

 always accompany exhaustion they should certainly be regarded as 

 contributory factors, which help to depress the vital powers according 

 to their prominence. It has been asserted, also, that the human organ- 

 ism has long been used to the frequent breathing of foul air, and will 



