HEAT IN RELATION TO THE HUMAN BODY 23 



ture in the lungs as cold air is inhaled, and to prevent death 

 by suffocation when temporary stoppage of the air passages 

 occurs. 



Air may be rebreathed repeatedly and continue to furnish 

 oxygen to maintain life. But it is to be remembered that 

 exhaled air containing available oxygen may be unfit for use 

 because of the carbon dioxide, water vapor, and waste organic 

 matter in it. The air as inhaled commonly consists of about 

 21 per cent oxygen, 78 per cent nitrogen, i per cent argon, 

 and 3/100 per cent carbon dioxide gas, along with a varialbe 

 quantity of water vapor and dust particles. The exhaeld 

 air is saturated with moisture, and has approximately 16 

 per cent oxygen and 5 per cent carbon dioxide, the argon 

 and nitrogen gases remaining unchanged in amount. About 

 one pint of water passes from the body daily as vapor in the 

 breath. 



The need of ventilation is often apparent to a person enter- 

 ing a schoolroom or public hall when those in the room are 

 unaware of the bad condition of the air. Dullness, rest- 

 lessness in body, headaches, inability to give continuous at- 

 tention, and much of the feeling of irritation experienced by 

 those shut up in schoolrooms oftentimes disappear after a 

 few minutes of exercise indoors with windows wide open. 

 It is to be remarked that cold air is not necessarily pure air, 

 rior do rooms need ventilating because they are comfortably 

 warm. Pure air, however, is no cure for late hours and in- 

 sufficient sleep, or for lack of wholesome food and absence 

 of other conditions essential to sound bodies and bright 

 minds. 



Artificial breathing in cases of drowning may, if necessary, 

 be successfully maintained for a long period by laying the 

 patient face down, the face turned to one side, and the mouth 

 open to admit free passage of air to and from the lungs. 

 Sitting astride the hips of the patient let some strong person 



