45 



Note the time at which digestion is completed in each tube. If the pepsin 

 is of U. S. P. strength, this should be at the end of six hours in tube 1, only a 

 few thin, insoluble flakes at most being left. From results obtained, determine 

 the relative strength of the pepsin. How many times its own weight of freshly 

 coagulated albumin will it digest in six hours ? 



153. Valuation of Commercial Pancreatin. Dissolve .28 gm. pancreatin 

 in lOOcc tepid water and add 1.5 gm. sodium bicarbonate. 



Place 5 cc. of the above solution in one test tube and "10 cc. in a second. Heat 

 some fresh cow's milk on a water bath, to 38-40 degrees, and add 20 cc. of this 

 milk to each test tube. Keep at 38-40 degrees for 30 minutes or longer. Test 

 small portions of each from time to time with Heller's cold nitric acid test. At 

 the end of 30 minutes, no coagulum should be produced in tube one, if the pan- 

 creatin is of standard strength. Note the time at which no coagulum is produced 

 in each tube. Repeat the experiment if necessary, using a larger or smaller 

 amount of pancreatin solution as indicated by above tests to digest 20 cc. milk 

 in 30 minutes. From amount of pancreatin solution necessary for this, calcu- 

 late its relative value. 



Using a 1^ starch solution, determine how many times its weight of starch 

 the pancreatin will digest in 30 minutes. 



154. Succus Entericus. — Invertase or (invertin) sugar split- 

 ting enzyme. This exists in the succus entericus or intesti- 

 nal juice and the mucous membrane of the small intestine, 

 which splits up cane-sugar and maltose into dextrose and 

 levulose. A molecule of cane-sugar or maltose takes up a 

 molecule of water, and splits into two molecules — one of dex- 

 trose, the other of levulose (fructose.) 



Ci2 H22 Oil + H^O = Cj Hjj O5 + Cg H12 Og. 

 Cane Sugar Dextrose Levulose. 



A similar enzyme can be extracted from yeast and many 

 plants. 



An extract of invertase may be made from the small in- 

 testine by adding to each gram of the mucous membrane used 

 1 cc. of 1% acetic acid, triturating in the mortar and adding 

 10 cc. of chloroform for each gram of the mucous membrane. 

 Let the mixture stand for a day or two and before using make 

 slightly alkaline by the addition of 1% sodium carbonate. 



155. Place 10 cc of a 10% solution of cane sugar in a 

 test tube and add 2 cc. of the extract of invertase. Allow the 

 mixture to digest at 40°C. After a short time test with 

 Fehling's solution for reducing sugars. 



