ACTION OF GASTRIC JUICE. 207 



test tubes. Set D and E in ice-water. To B add a few 

 drops of hydrochloric acid. Set A, B, and C in water kept 

 at 100 F. After ten minutes, test A, B, C, and D as in 

 Exp. 2. In A boiling destroyed the power of the saliva. In 

 B the acid prevents action as in the stomach. C shows grape 

 sugar. D shows no change. 



5. Transfer E to warm water for ten minutes, then test to 

 show that cold has not killed the saliva, but merely arrested 

 its action. 



6. Test the action of saliva on raw starch, conditions as 

 in C. 



1. Test both the saliva and the starch separately, to show 

 that there is no sugar in them. 



The action of the Gastric Juice. 



Buy some pepsin of the druggist. Boil an egg hard, and 

 thoroughly mince part of the white, best by rubbing it through 

 a sieve. Add pepsin to a little of the egg in each of four 

 test tubes half full of water. Label A, B, C, and D. To B 

 add bicarbonate of soda, to C and D a few drops of dilute 

 hydrochloric acid. Set A, B, and C in warm water, and D in 

 ice-water. Shake the tubes frequently. 



Eepeat C with large pieces of egg to see the effects of 

 imperfect mastication. 



Try also pepsin that has been boiled. 



Pepsin may be obtained by dissecting off the mucous coat 

 of a pig's stomach, mincing, and soaking it in glycerin for a 

 day or two, and straining. 



Action of the Pancreatic Juice. 



The pancreatic juice may be extracted from a fresh pan- 

 creas (taken from a pig) by mincing the pancreas, and soaking 

 it in water for a few hours. But it will probably be more 

 satisfactory to buy from the druggist preparations of Pancre- 

 atin and Amylopsin. 



