The Necessity of Pure Air for Health. 255 



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From the skin, 10 grammes of carbonic acid with an 

 undetermined quantity of various salts and organic 

 matter are excreted. The same weight, 10 grammes, of 

 oxygen is given as the amount absorbed by the skin. 

 This total amount of carbonic acid (910 grammes) re- 

 quires 72,000 cubic feet of fresh air for its proper dilution 

 and the water (25 to 40 ozs.) a varying quantity depending 

 on the hydrometric condition of the air, and the 

 temperature. 



Organic matters are also given off from the lungs, 

 mouth and skin, comprising dead epithelium, fatty and 

 other matters, but the exaft quantity has never yet been 

 accurately determined. The organic matter from the 

 lungs is the most important, of which the following is 

 known. It is a nitrogenous and oxidisable body with an 

 offensive odour. It commonly floats in clouds and is 

 not a gas, but has a molecular formation. It is highly 

 poisonous, for administered to a mouse, Parkes states 

 that it killed in 40 minutes. It is this that makes a room, 

 a bedroom more especially, offensive and stuffy. If 

 respired air be drawn through water, the water then set 

 aside for a few hours, a most offensive odour is developed, 

 due to the organic matter absorbed by the water from 

 the breath. If this organic matter be burnt it gives an 

 odour as of burning animal matter. 



Taking '04 as the quantity of carbonic acid gas nor- 

 mally present in ordinary air, it is found that when it is 

 raised to "06 by respiration in a room, the odour of 

 organic matter becomes perceptible to all entering from 

 the open air. This added -02 of carbonic acid must be 

 taken, and is taken by sanitarians, as the limit of allow- 

 able impurity. In order that this limit shall not be 



