PANCREATIC DIGESTION. 57 



have been prepared each with a view to obtaining predominat- 

 ing reactions for the specific enzyme. (See Appendix.) 



TRYPSIN AND TRYPSINOGEN. 



Trypsin is active in an alkaline, faintly acid or neutral 

 solution, but its maximum reaction occurs in a 1 per cent 

 solution of Na 2 C0 3 . It is killed at a temperature about 

 55 C. 



Use the proteolytically active pancreatic extract and 

 prepare test-tube digestions in the water-bath at 40 C., as 

 under gastric digestion. 



(a) Fibrin + 5 c.c. of the pancreatic extract. 



(6) " +5" " " " " + 2 c.c. 0.5% 



Na 2 C0 3 . 



Compare the manner of action of the trypsin upon the 

 fibrin to that of the pepsin. 



(c) Fibrin + 5 c.c. of 0.5% Na 2 CO 3 . 



(d) " + 5 " " " " li +5 c.c. pancreatic ex- 

 tract which has been previously boiled and cooled. 



TRYPTIC PROTEOLYSIS. 



As regards its proteolytic activity, the enzyme trypsin 

 is more energetic and far-reaching than pepsin. Conse- 

 quently in pancreatic digestion there takes place a more 

 rapid and deep-seated cleavage of the protein molecule 

 than is possible in the stomach. Proteoses and peptones 

 are formed in the middle stages of the digestion, but these 

 are rapidly carried over into substances with a relatively 

 small molecular weight which do not give the biuret reaction 

 and consequently cannot be termed peptones. It is now 

 considered that the end products of a long-continued tryptic 

 digestion of the ordinary proteins comprise the amino-acids, 



