92 EXPERIMENTAL PHYSIOLOGY 



temperature. How does the temperature of the expired air 

 compare with that of the body, or blood temperature? Test 

 this on several successive days and note whether the tem- 

 perature varies with the external temperature or is con- 

 stant. 



B. Composition. Breathe on a piece of glass. What col- 

 lects on the surface? Does expired air contain more or less 

 moisture than inspired air? 



Fill the test tube half full of limewater and blow the 

 breath gently through it by means of the glass tube. What 

 change takes place in the limewater? What does this in- 

 dicate? (See Ex. V.) 



Fill the bottle with expired air by the method of Ex. II. 

 Turn the bottle mouth upward and introduce a lighted 

 match into it. Does the match continue to burn? What 

 does this indicate? (Air expired in ordinary breathing has 

 lost about one-fourth of the oxygen contained in the air 

 inspired.) 



