TRYPSIN DIGESTION. 483 



but the nature of the protein is also of importance. The reports in 

 regard to the action of trypsin in various reactions are still somewhat 

 disputed. 1 The action of the alkali depends upon the number of hydroxyl 

 ions (DIETZE, KAXITZ), and according to KANITZ 2 the digestion pro- 

 ceeds best in those solutions which are 1/70-1/200 normal in regard 

 to hydroxyl ions. Free mineral acids, even in very small quantities, 

 completely prevent the digestion. If the acid is not actually free, but 

 combined with protein bodies, then the digestion may take place quickly 

 when the acid combination is not in too great excess (CHITTENDEN and 

 CUMMINS). Organic acids act less disturbingly, and in the presence 

 of 0.2 p. m. lactic acid and the simultaneous presence of bile and common 

 salt the digestion may indeed proceed more quickly than in a faintly 

 alkaline liquid (LINDBERGER). The assertion of RACHFORD and SOUTH- 

 GATE, that the bile can prevent the injurious action of the hydrochloric 

 acid, and that a mixture of pancreatic juice, bile > and hydrochloric acid 

 digests better than a neutral pancreatic juice, could not be substantiated 

 by CHITTENDEN and ALBRO. That bile has an action tending to aid the 

 tryptic digestion has been shown by many investigators, and recently 

 by BRUNO, ZUNTZ and Ussow and others. 3 



Carbon dioxide, according to ScniERBECK, 4 has a retarding action in 

 acid solutions, but it accelerates the tryptic digestion in faintly alkaline 

 liquids. Foreign bodies, such as potassium cyanide, may promote tryptic 

 digestion, while other bodies, such as salts of mercury, iron, and others 

 (CHITTENDEN and CUMMINS), or salicylic acid in large quantities, may 

 have a preventive action. According to WEISS 5 the halogen alkali 

 salts disturb tryptic digestion only slightly, and NaCl seems to have 

 the strongest action. The sulphates have a much stronger retarding 

 action than the chlorides. The nature of the proteins is also of impor- 

 tance. Unboiled fibrin is, relatively to most other proteins, dissolved 

 so very quickly that the digestion test with raw fibrin gives an incor- 

 rect idea of the power of trypsin to dissolve coagulated protein bodies 

 in general. Boiled fibrin is digested with much greater difficulty and 

 also requires a higher alkalinity: 8 p. m. Na 2 COs (VERNON 6 ). The resist- 

 ance of certain native protein solutions, such as blood-serum and egg- 



1 See Kudo, Bioch. Zeitschr., 15. 



2 Kanitz, Zeitschr. f. physiol. Chem., 37, who also cites Dietze. 



3 Chittenden and Cummins, Studies from the Physiol. Chem. Laboratory of Yale 

 College, New Haven, 1885, 1, 100; Lindberger, Maly's Jahresber., 13; Rachford and 

 Southgate, Medical Record, 1895; Chittenden and Albro, Amer. Journ. of Physiol., 1, 

 1898; Rachford, Journ. of Physiol., 25; Bruno, 1. c.; Zuntz and Ussow, Arch. f. (Anat. 

 u.) Physiol., 1900. 



4 Skand. Arch. f. Physiol., 3. 



5 Weiss, Zeitschr. f. physiol. Chem., 40. See also Kudo, 1. c. 

 e Journ. of Physiol., 28. 



