PANCREATIC DIGESTION. 145 



cloth, filter, nearly neutralize with potassium hydroxide solution 

 and then exactly neutralize it with 0.5 per cent sodium carbonate. 



PRODUCTS OF TRYPTIC DIGESTION. 



Take about 200 grams of lean beef which has been freed from 

 fat and finely ground and place it in a large-sized beaker. Intro- 

 duce equal volumes of the pancreatic extract prepared as above 

 and 0.5 per cent sodium carbonate, add 5 c.c. of an alcoholic solu- 

 tion of thymol to prevent putrefaction, and place the beaker in 

 an incubator at 40 C. Stir the contents of the beaker frequently 

 and add more thymol if it becomes necessary. Allow digestion 

 to proceed for from 2 to 5 days and then separate the products 

 formed as follows : Strain off the undissolved residue through 

 cheese cloth, nearly neutralize the solution with dilute hydrochloric 

 acid and then exactly neutralize it with 0.2 per cent hydrochloric 

 acid. A precipitate at this point would indicate alkali metaprotein 

 (alkali albuminate). Filter off any precipitate and divide the fil- 

 trate into two parts, a one-fourth and a three-fourth portion. 



Transfer the one-fourth portion to an evaporating dish and 

 make the separation of proteases and peptones as well as the final 

 tests upon these bodies according to the directions given on page 114. 



Place about 5 c.c. of the three-fourth portion in a test-tube and 

 add about i c.c. of bromine water. A violet coloration indicates the 

 presence of tryptophane (see page 73). Concentrate 1 the remain- 

 der of the three-fourth portion to a thin syrup and make the sep- 

 aration of leucine and tyrosine according to the directions given on 

 page 82. 





GENERAL EXPERIMENTS ON PANCREATIC 

 DIGESTION. 



EXPERIMENTS ON TRYPSIN. 



i. The Most Favorable Reaction for Tryptic Digestion. 



Prepare seven tubes as follows : 



(a) 2-3 c.c. of neutral pancreatic extract -f- 2 ~3 c.c. of water. 



(b) 2-3 c.c. of neutral pancreatic extract + 2-3 c.c. of i per 

 cent sodium carbonate. 



(c) 2-3 c.c. of neutral pancreatic extract + 2-3 c.c. of 0.5 per 

 cent sodium carbonate. 



1 If the solution is alkaline in reaction, while if is being concentrated, the 

 amino acids will be broken down and ammonia will be liberated, 

 ii 



