Respiration 349 



across the window sill with the lower sash slightly raised. This 

 throws the air current upward and prevents its blowing directly 

 on the occupants of the room. 



The placing of a muslin screen over a window opening will 

 prevent too strong a draft and yet permit a sufficient flow of air 

 into a room. 



An open fireplace is desirable in every living room. As soon 

 as the fire is lighted, the current of air up the chimney 

 draws the stale air from the room. Thi's air is quickly replaced 

 by fresh air that will enter through any opening, however 

 small. 



The problem of securing adequate ventilation in public halls, 

 school rooms, and large buildings is an important one. Modern 

 ideas of ventilation demand the removal of all unhealthy gases 

 and odors, the introduction of a certain amount of moisture, 

 the constant movement of the air, and the maintenance of a 

 proper temperature, as well as the introduction of fresh air. It 

 is often necessary to force air into the rooms by motor-driven 

 fans in the basement, through a humidifier, which moistens the 

 air. 



Hot air pipes in ventilating flues and revolving fans placed at 

 the top of the flues are used to draw out the impure air. These 

 devices must work in harmony with the heating plant of the build- 

 ing in order to secure the right temperature. When the entire 

 system works as it should, the foul air and dust will be eliminated 

 from the building and its place taken by a constant flow of fresh 

 air, properly moistened and warmed. 



Experiments Related to Respiration. 



Experiment to Prove That Heat Is Generated in the 

 Body. Note the temperature of the room. Place a clinical 

 thermometer under your tongue to find the temperature of your 

 body. Now exercise violently for two minutes. Again take the 

 temperature of your body. Has it increased? Has the tempera- 

 ture of the room increased? Do you conclude that heat is gen- 

 erated in the body? 



Experiment to Show That Carbon Dioxide Is Produced 

 in the Body. Breathe into a test tube or bottle of lime water. 



