I0 2 THE VITAL PROCESSES 



size each one fourth full of limewater and fit each with a two-holed rubber 

 stopper (Fig. 50). Fit into each stopper one short and one long glass 

 tube, the long tube extending below the limewater. Connect the 

 short tube of one bottle and the long tube of the other bottle with 

 a Y-tube. Now breathe slowly three or four times through the Y-tube. 

 It will be found that the inspired air passes through one bottle and the 

 expired air through the other. Compare the effect upon the lime- 

 water in the two bottles. Insert a small burning splinter into the top 

 of each bottle and note result. What differences between inspired and 

 expired air are thus shown? 



3. Blow the breath against a cold window pane. Note and account 

 for the collection of moisture. 



4. Note the temperature of the room as shown by a thermometer. 

 Now breathe several times upon the bulb, noting the rise in the mer- 

 cury. What does this experiment show the body to be losing through 

 the breath? 



To show Changes in the Thoracic Cavity. i. To a yard- or meter- 

 stick, attach two vertical strips, each about eight inches long, as shown 



FIG. 51. Apparatus for measuring chest expansion. 



in Fig. 51. The piece at the end should be secured firmly in place 

 by screws or nails. The other should be movable. With this con- 

 trivance measure the sideward and forward expansion of a boy's thorax. 

 Take the diameter first during a complete inspiration and then during 

 a complete expiration, reading the difference. Compare the forward 

 with the sideward expansion. 



2. With a tape-line take the circumference of the chest when all 

 the air possible has been expelled from the lungs. Take it again when 

 the lungs have been fully inflated. The difference is now read as the 

 chest expansion. 



To illustrate the Action of the Diaphragm. Remove the bottom 

 from a large bottle having a small neck. (Scratch a deep mark with a 



