A YEAE IN SCIENCE HI 



A. Pepsin. 



Make a weak solution of pepsin by dissolving a few 

 grams of pepsin in 50 c.c. of water. 



Prepare five test tubes as follows : 



In the first, place a small amount of starch paste, 

 10 c.c. of pepsin, and a few drops of very dilute hydro- 

 chloric acid. Label tube No. 1. 



In the second, place a few pieces of egg-white,- 10 c.c. 

 of pepsin, and dilute hydrochloric acid. Label No. 2. 



In the third, place a few pieces of egg-white, 10 c.c. 

 of pepsin, and a few drops of very dilute sodium 

 hydroxide solution (0.2%). Label No. 3. 



In the fourth, place 5 c.c. of olive oil, 10 c.c. of pep- 

 sin, and a few c.c. of dilute hydrochloric acid. Label 

 No. 4. 



Shake the tubes and keep them at a temperature of 

 36 C. for 24 hours. At the end of that time test the 

 contents of the tubes. 



Test No. 1 for starch and sugar. 



In No. 2, has the egg-white dissolved? 



In No. 3, has the egg-white dissolved? 



In No. 4, is there any change in the olive oil ? 



Upon which foodstuffs does pepsin act? 



In comparing tubes No. 2 and No. 3 does pepsin act 

 in a base or acid solution? 



B. Rennin. 



In the fifth tube place 10 c.c. of milk and 5 c.c. of 

 rennet (which contains rennin). Set aside for 30 



