506 DIGESTION. 



Liss follows the digestion by the electrical conductivity, and F. WEISS 1 determines 

 the quantity of nitrogen not precipitated by tannic acid. The formol titration 

 can also be used with advantage for determining the decomposition (page 166). 



The reaction has a great influence upon the rapidity of the trypsin 

 digestion. Trypsin acts energetically in neutral, or still better in alkaline, 

 solutions, and according to older statements, best in an alkalinity of 

 3-4 p. m. Na2COs; 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. 2 The action of the alkali depends upon the 

 number of hydroxyl ions (DIETZE, KANITZ), and according to KANITZ S 

 the digestion proceeds 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 RACH- 

 FORD and SOUTHGATE, 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. 4 

 Carbon dioxide, according to SCHIERBECK, S has a retarding action 

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

 alkaline liquids. Foreign bodies, such as potassium cyanide, may pro- 

 mote tryptic digestion, while other bodies, such as salts of mercury, iron, 

 and others (CHITTENDEN and CUMMINS), or salicylic acid in large quan- 

 tities, may have a preventive action. According to WEISS 6 the halogen 



1 Weiss, Zeitschr. f. physiol. Chem., 40; Lohlein, Hofmeister's Beitrage, 7; Jacoby, 

 Bioch. Zeitschr., 10; Gross, Arch. f. exp. Path. u. Pharm., 58; Bayliss, Arch, des 

 scienc. biol. de St. Pe"tersbourg, 11, Suppl.; and Journ. of Physiol., 36; Weiss, Zeitschr. 

 f. physiol. Chem. 31, 78 (1900). 



2 See Kudo, Bioch. Zeitschr., 15. 



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



4 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. 



5 Skand. Arch. f. Physiol., 3. 



6 Weiss, Zeitschr. f. physiol. Chem., 40; See also Kudo, Bioch. Zeitschr. 15, 473 

 (1908). 



