272 DIGESTION, CIRCULATION, AND ABSORPTION 



Observations. 1. Does the grape sugar dissolve in water ? 



2. What color is produced by boiling when Fehling's solu- 

 tion is added ? 



Conclusions. 1. How determine whether grape sugar dis- 

 solves in water ? 



2. Review the test for the presence of grape sugar. 



Method c. Add some fresh saliva 1 to a small amount (| test 

 tube full) of diluted starch paste. Set it aside in a warm place, 

 for ten minutes or more. Then test for grape sugar. 2 Test some 

 of the saliva for grape sugar and likewise test the starch paste. 



Observations. 1. What effect when Fehling's solution and 

 saliva are boiled ? 



2. What effect when starch paste and Eehling's solution are 

 boiled ? 



3. What effect when the mixture of starch paste and saliva 

 are boiled with Fehling's solution ? 



Conclusions. 1. Is there any grape sugar present in the 

 saliva ? Is there any grape sugar present in the starch paste ? 



2. Is there any grape sugar in the mixture of starch paste 

 and saliva after standing for a short time ? 



3. How can you account for the sugar in the starch paste 

 after treating it with saliva ? 



4. What is the effect upon the solubility of starch after 

 treating it with saliva ? 



5. What is digestion ? 



6. Chew a piece of cracker slowly. Can you account for 

 the sweetish taste ? (Homework.) 



b. In the Stomach 



1. ACTION OF GASTRIC JUICE (OPTIONAL) 



Materials. Minced white of boiled egg, hydrochloric acid, pepsin, 5 

 numbered test tubes, beaker, and cracked ice in a container. 



1 Fresh saliva may be procured by first rinsing the mouth, then chewing 

 Paraffin wax and collecting the saliva in a test tube. 



2 The sugar present is really maltose. The tests for the two sugars are the 



