A YEAE IN SCIENCE 109 



CHAPTER XVTII 



DIGESTION AND ABSORPTION 



Exercise 73. Digestion in the Mouth. 

 Object: To determine the foodstuffs acted upon by 

 saliva. 



Apparatus 



Litmus paper Iodine 



Corn starch Test tube 



Egg-white Test tube rack 



Olive oil Test tube clamp 



Hydrochloric acid Bunsen burner 

 Fehling's solution 



Directions: Food is first acted upon by a fluid, 

 saliva, which is secreted by glands discharging into 

 the mouth. Test saliva by placing a piece each of red 

 and blue litmus paper upon the tongue. Is saliva acid 

 or base? Dry the mouth as much as possible by swal- 

 lowing and then place on the top of the tongue a pinch 

 of salt. Can you taste the salt? Keep the salt on the 

 tongue for a minute. What happens to the salt? 

 Can you now taste it? 



To determine the chemical action of saliva on the 

 foodstuffs, prepare test tubes as follows : 



In the first, place a small amount of thin starch 

 paste, to which add a few c.c. of saliva. Label No. 1. 



In the second, place some starch paste and saliva, 

 to which add a few drops of hydrochloric acid. Label 

 No. 2. 



