GASTRIC DIGESTION 317 



7. Arrange six test tubes as follows, numbering them Nos. 

 1 to 6, and labelling with your name. 



1. 5 c.c. distilled water. 



2. 5 c.c. 0.2% hydrochloric acid. 



3. 5 c.c. water -f- 10 drops glycerine extract of 

 pig's stomach prepared above. 



4. 5 c.c. 0.2% HC1 -f- 10 drops glycerine extract. 



5. 5 c.c. 0.2% HC1 -|- 10 drops glycerine extract, 

 boil thoroughly 3 or 4 minutes and cool. 



6. 5 c.c. 0.3% sodium carbonate -j- 10 drops glyc- 

 erine extract. 



In each tube suspend a Mett tube by means of a thread 

 supported by a match. Make sure that the Mett tube hangs 

 so that it does not touch the bottom of the test tube. The 

 digestion liquid must have free access to the egg white.' Place in 

 the incubator until the next period. After a minimum time of 24 

 hours, compare the amounts of digestion in the different tubes 

 and record results. Why does not No. 3 digest? 



8. ON MILK. The ferment rennin, by some investigators con- 

 sidered to be identical with pepsin, causes the clotting of milk 

 due to precipitation of casein. Calcium salts are necessary for 

 this process. Prepare two test tubes each containing 5 c.c. of 

 milk. 



1. To one add 3 c.c. ammonium oxalate. 



2. To the second add 3 c.c. distilled water. 



As the rennin in the glycerine extract is very likely to have 

 become inactive, .powder a rennin tablet and add half of the 

 powder to each tube. 



Place the tubes in water at 40 for 20 minutes. What hap- 

 pens? Explain. To the oxalate tube add 3-4 drops of con- 

 centrated calcium chloride solution. Explain. 



Gastric juice contains also a lipase, but its action is not 

 extensive. 



9. PRODUCTS OF GASTRIC DIGESTION. When the hydrochloric 

 acid stomach mucosa mixture has remained in the incubator for 

 2 or 3 days or longer, remove it, boil, filter and neutralize the 



