58 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



viz., leucine, tyrosine, aspartic and glutamic acids; the hexone 

 bases, viz., arginine, lysine, and histidine; the so-called trypto- 

 phane or proteinochromogen, which is an indole derivative ; and 

 probably other bodies whose nature is not well understood. 



Prepare a pancreatic digestion as follows: 



Place in a large flask (5-10 liters) 500-1000 grms. of 

 fibrin, a liter of an infusion of Kuhne's dried pancreas, and 

 1000-2000 c.c. of 0.25 per cent Na 2 C0 3 ; add plenty of chloro- 

 form or powdered thymol, and allow the mixture to digest at 

 40 C. for at least a week. 



At the end of this time the solution is exactly neutralized 

 with dilute H 2 S0 4 and concentrated to about one-half its 

 volume; it is then filtered. From the filtrate the proteoses 

 are removed by saturation with (NH 4 ) 2 S0 4 in a nearly 

 boiling solution. These are filtered off and tho filtrate still 

 further concentrated. During this procedure relatively 

 large quantities of leucine and tyrosine should crystallize out 

 of the mixture along with the (NH 4 ) 2 S0 4 . These must be 

 filtered off and the (NH 4 ) 2 S0 4 removed from the filtrate by 

 means of Ba(OH) 2 and BaC0 3 . The BaS0 4 is again re- 

 moved by filtration and to the new filtrate dilute H 2 S0 4 

 added to just precipitate the excess of Ba in the solution. 

 After filtration the solution will contain the hexone bases. 



Compare the quantities of proteoses and peptones ob- 

 tained in this digestion with those from the peptic proteolysis. 



TYROSINE, CH 2 -CH-COOH. 



Use the crystals obtained in the pancreatic digestion. 



(a) Examine them under the microscope. 



(6) Try to dissolve some in cold, then warm water. Then 



