46 LABORATORY EXERCISES. 



the tubes of sheep's intestine,* moisten it, and 

 tie it tightly over the larger end of the thistle- 

 tube/ taking care that none of the grape-sugar 

 solution escapes. Stand the thistle-tube (mem- 

 brane down) in a glass bottle filled with water 

 up to the level of the grape-sugar solution. 

 Mark on the bottle the level of the two liquids. 

 Connect a long piece of glass tubing to the 

 smaller end of the thistle-tube and support it 

 in a vertical position. (The experiment can 

 be demonstrated better in a large class-room 

 if a little red ink is dropped on the top of the 

 grape-sugar solution.) (See Fig. 4.) 



1. At the end of several hours notice the level 



reached by the liquid within the thistle- 

 tube. Measure the difference between 

 the level of the liquid within the thistle- 

 tube and the level of the liquid in the 

 bottle. 



2. Remove with a glass-tube some of the water 



on the outside of the thistle -tube (in the 

 bottle). Test it with Fehling's solution. 

 What is the result? How do you ac- 

 count for this result? 



3. Which of the two liquids (the water in the 



bottle or the grape-sugar solution in the 



* Parchment paper may be used instead of the dried sheep's in- 

 testine to cover the end of the thistle-tube. Or a membrane may 

 be obtained which will answer the purpose by dissolving the mineral 

 portion of an egg-shell, leaving the lining membranes intact; the 

 membrane may then be tied to the end of the tube 



