116 LABORATORY EXERCISES 



b. When ycfu are breathing quietly and regularly, count the 

 number of inspirations in a minute, and record them. Find 

 out the number for another person of your own age ; for a young 

 child. Count your respirations after violent exercise. 



c. With a measuring tape get the distance around your 

 chest. To do this, pass the tape across your back and just 

 under your arm-pits; bring it together just over your breast 

 bone. Now breathe very deeply, and get the chest measure. 

 Finally exhale all the air you possibly can, and get your chest 

 measure. What is the difference between the last two results? 

 This represents your chest expansion. 



d. Find how many cubic centimeters of air you can expel: 

 (1) from lungs that are normally full of air; (2) from lungs 

 that are as full as you can make them. The apparatus 

 needed is a 2-quart glass fruit-jar, a pan of water, and a tube, 

 as in Fig. 37, 45, of the text. You will need to know the 

 capacity of the jar and the volume of water left after each trial. 

 Results? 



e. You can show by simple means how the action of the 

 diaphragm aids in bringing air into the lungs and in expelling 

 it from the lungs. You need a small-mouth bottle from which 

 the bottom has been removed (see Exercise 84). This form of 

 the apparatus is suggested in Walters' Physiology and Hygiene. 

 Set the bottle, right side up, in water that is about half as deep 

 as the bottle is tall. Let the level of the water represent the 

 diaphragm. As you raise the bottle, the water level falls, and 

 air rushes into the bottle's mouth. This represents an inspira- 

 tion. As you lower the bottle, the water level rises, and air is 

 expelled; this represents an expiration. The results are seen 

 better if a piece of smoking " touch paper" is held over the 

 mouth of the bottle. To make touch paper, soak strips of 

 filter paper or blotting paper in a solution of potassium nitrate 

 (saltpeter), and dry them. 



