22 



EXPERIMENTAL PHYSIOLOGY 



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posts as indicated in Fig. 8. Note what happens. Where do 

 the bubbles form? In which tube do they form most rapidly? 

 What is the ratio by volume of the 

 gases in the two tubes? 



When the tube containing the most 

 gas is full, disconnect the cells. Collect 

 in a test tube the gas from the tube 

 containing thelesser amount as follows: 

 With rubber connecting tubing connect 

 an ordinary delivery tube, filled with 

 water, to the top of the gas tube. 

 Insert the end of the delivery tube 

 into the mouth of the test tube, after 

 filling the test tube with water and in- 

 verting as in Ex. II. Open the cock 

 and collect the gas as in Fig. 9. Cover 

 the mouth of the tube with the thumb 

 and hold mouth upward. Now re- 

 move the thumb and quickly insert a hghted sphnter into 

 this collected gas. What happens? What gas have you 



studied that produces a 

 similar action? This is 

 the same gas. 



In a second test tube 

 collect the gas in the 

 other tube. Hold it 

 mouth downward, and 

 introduce a hghted sphn- 

 ter into it. Describe 

 what happens. How is this gas different from oxygen? 

 from nitrogen? (The name of this new gas is hydrogen. 

 The electric current has broken the compound — ^water — 



Fig. 8. 



Fig. 9. 



