10 PHYSIOLOGICAL CHEMISTRY. 



separate and identify the end-products of the action of pancreatic 

 protease according to the directions given on p. 145. 



5. Demonstration of a Vegetable Protease. A commercial 

 preparation of papain (papayotin, carase or papase), the protease 

 of the fruit of the pawpaw (carica papaya), may be used in this 

 connection. Follow the same procedure as that described under 

 gastric protease (see p. 9). 



III. LIPASES. 



1. Preparation of Pancreatic Lipase. 1 An extract of this en- 

 zyme may be prepared from the pancreas of the pig or sheep ac- 

 cording to the directions given on p. 144.2 



2. Demonstration of Pancreatic Lipase. Into each of two 

 test-tubes introduce 10 c.c. of milk and a small amount of litmus 

 powder. To the contents of one tube acid 3 c.c. of a neutral ex- 

 tract of pancreatic lipase and to the contents of the other tube add 

 3 c.c. of a boiled neutral extract of pancreatic lipase. Keep the 

 tubes at 38 C. and watch for color changes. The blue color of 

 the litmus powder will gradually give place to a red. This change 

 in the color of the litmus from blue to red has been brought about 

 by the fatty acid which has been produced through the lipolytic ac- 

 tion exercised by the lipase upon the milk fats. 



3. Preparation of Vegetable Lipase. This enzyme may be 

 readily prepared from castor beans, several months old, by the fol- 

 lowing procedure: 3 Grind the shelled beans very fine 4 and ex- 

 tract for twenty-four hour periods with alcohol-ether and ether, in 

 turn. Reduce the semi-fat-free material to the finest possible con- 

 sistency by means of mortar and pestle and pass this material 

 through a sieve of very fine mesh. Place this material in a Soxhlet 

 extractor and extract for one week. This fat-free powder may 

 then be used to demonstrate the action of vegetable lipase. Powder 

 prepared as described may be used in quantitative tests. For ordi- 

 nary qualitative tests it is not necessary to remove the last traces 

 of fat and therefore the extraction period in the Soxhlet apparatus 

 may be much shortened. 



1 Also called steapsin. For a discussion of this enzyme see p. 143. A very 

 active lipolytic extract may also be prepared from the liver. 



2 If preferred a glycerol extract may be prepared according to the directions 

 given by Kanitz ; Zeitschrift fur physiologische Chemic, 1906, XLVI, p. 482. 



3 A. E. Taylor: On Fermentation; University of California Publications, 1907. 

 *The shells should be removed without the use of water. These beans are 

 poisonous due to their content of ricin. 



