86 AIR 



Experiment 42. The Capacity of the Lungs. 



Apparatus: Large bottle, holding at least a gallon, 

 cork stopper to fit, large pan, holding at least two gallons, 

 piece of rubber tubing three feet long, piece of glass 

 tubing which has had its rough edges rounded off in a 

 flame. 



a. Fill the bottle full of water, insert the stopper 

 and invert in a pan in which there is about two quarts of 

 water. Remove the stopper and slip one end of the 

 rubber tubing up into the bottle, which should be tipped 

 a little to one side, and held there, in order not to jam the 

 tubing. The glass tubing should be inserted in the other 

 end of the rubber tubing to serve for a mouthpiece, which 

 may be washed before each pupil uses it. Take several 

 long breaths before measuring your lung capacity. Then 

 take the longest breath possible, place the tube in the 

 mouth, and blow hard. Keep on blowing until you can- 

 not exhale a bubble more. Immediately remove the 

 rubber tube from the bottle and estimate your lung 

 capacity. There are 231 cubic inches in a gallon. If 

 100 cubic inches of air still remained in your lungs, what 

 is the capacity of your lungs? 



The amount of air which is needed per minute, in a 

 room in which there are several persons, cannot be found 

 out by multiplying the number of cubic inches used in 

 each breath by the number of breaths per minute, and 

 by the number of persons in the room. We must remem- 

 ber that the air which we exhale contains four hundred 

 parts of carbon dioxide in ten thousand, while the proper 



