RESPIRATION 387 



causing a cough and rendering it more liable to inflammation. 

 If inhaled into the bronchi, it produces still greater irritation, 

 and the vaporized nicotine is more readily absorbed as the smoke 

 is inhaled the more deeply. Cigarettes contain the same poisons 

 as other forms of tobacco, and often contain other poisons which 

 are added to flavor them." — Overton, Applied Physiology. 



Need of Ventilation. — During the course of a day the lungs have lost 

 to the surrounding air nearly two pounds of carbon dioxide. This means that 

 about three fifths of a cubic foot is given off from each person during an 

 hour. When we are confined for some time in a room, it becomes neces- 

 sary to get rid of this carbon dioxide. This can be done only by means of 

 proper ventilation. Other materials are passed off from the lungs, with 

 carbon dioxide. It is the presence of these wastes in combination with 

 carbon dioxide that makes breathed air particularly unwholesome. It has 

 been determined that as little as one per cent carbon dioxide is injurious in 

 expired air, although a much greater percentage than this may be safely- 

 breathed if the carbon dioxide is introduced into fresh air. The presence of 

 impurities in the air of a room may easily be determined by its odor. The 

 "close" smell of a poorly ventilated room is due to organic impurities given 

 off with the carbon dioxide. This, fortunately, gives us an index by which 

 we may prevent poisoning. Air containing 8 parts of carbon dioxide to 

 10,000 parts of air is bad; while from 12 to 14 parts in 10,000 makes a 

 very dangerous amount. Among the factors which take oxygen fro in the 

 air in a closed room and produce carbon dioxide, are burning gas or oil 

 lamps, stoves, the presence of a number of people, etc. 



Proper Ventilation. — Ventilation consists in the removal of 

 air that has been used, and the introduction of a fresh supply to 

 take its place. If we remember that warm air is lighter than cold 

 air, and carbon dioxide is heavier than air, we can see that ventila- 

 tion outlets should be on the level of the floor. The inlets should 

 be near the top of the room, especially in houses heated by any 

 method of direct radiation, such as steam or hot water. A good 

 method of ventilation for the home is obtained by placing a board 

 two or three inches high between the lower sash and the frame of 

 a window. 



Sweeping and Dusting. — It is very easy to demonstrate the 

 amount of dust in the air by following the course of a beam of 

 light in a darkened room. We have already proved that spores 

 of mold and yeast exist in the air. That bacteria are also present 



