RESPIRATION 389 



large amount of water vapor and heat, together with a very little 

 organic waste matter. 



Ventilation. The fact that air in a " close " room becomes un- 

 fit to breathe, is due mainly to the excess moisture and heat, and 

 not to the carbon dioxide, or lack of oxygen, as was formerly sup- 

 posed. 



The carbon dioxide in the expired air is produced by the oxygen 

 from the lymph uniting with the carbon of the tissues. The water 

 is produced by oxidation of their hydrogen, and the heat is the 

 result of both oxidation processes. We use annually about 10,000 

 pounds of air (28.7 pounds per day) from which we take about 

 650 pounds of oxygen and give off about 730 pounds of carbon 

 dioxide. We breathe out about 9 ounces of water every day, which 

 would make half a pint in liquid form. These figures, while not 

 worth remembering, will give some idea of the amount of work 

 done by the respiratory organs and their importance to our life. 



Proper ventilation is concerned, not only with supplying " fresh " 

 air, but with the removal of water vapor, heat, and least of all, 

 carbon dioxide. Here circulation of air in a room will often relieve 

 breathing conditions, by lowering the body temperature and re- 

 moving excess water vapor from the vicinity of the body. We 

 usually have oxygen enough in any ordinary air supply, and seldom 

 does the carbon dioxide cause trouble, but very often the tem- 

 perature and amount of water vapor produce unpleasant and even 

 dangerous results. 



COLLATERAL READING 



Physiology Textbook, Colton, pp. 105-137; General Physiology, Eddy, 

 pp. 312-339; Applied Physiology, Overton, pp. 206-219; Human Mecha- 

 nism, Hough and Sedgwick, pp. 162-176; Human Body and Health, Davison, 

 pp. 132-162; Studies in Physiology, Peabody, pp. 209-231; Human Body, 

 Martin, pp. 193-214; Elementary Physiology, Huxley, pp. 148-191; High 

 School Physiology, Hughes, pp. 179-196; 



