HEAT IN RELATION TO THE HUMAN BODY 19 



PURE AIR AND BREATHING 1 



In order to keep warm and dry men require shelter from 

 the weather. The occupations of many people keep them 

 within doors the year around. As a matter of economy and 

 of comfort during the winter season, dwellings and places of 

 business are guarded against the entrance of the cold outer air. 

 This shuts away the supply of oxygen essential to health. 

 A single gas light exhausts the oxygen of a room and produces 



FIG. 7. Sleeping porch, and sun parlor. 



carbon dioxide as fast as the breathing of several persons. 

 So far as need of air is concerned man is an out-of-door ani- 

 mal. The conditions of civilized life have shut him in so 

 closely that health is often impaired, and life itself sometimes 

 sacrificed. 



About one-third of a person's life should be spent in sleep. 

 For sleep to be most refreshing and invigorating it should be 

 in rooms or porches wide open to the out-of-doors air. Only 



1 Respiration as the term is used in biology involves the process of oxidation 

 as it occurs in the cells. It is a function of living cells wherever located. On 

 the other hand the term breathing is restricted to the exchange of gases within 

 and without plants and animals, and is a purely physical process. 



