482 DIGESTION. 



liquid. Tryptic digestion differs essentially from pepsin digestion, irre- 

 spective of the difference in the digestive products, in that the first takes 

 place in neutral or alkaline reaction and not, as is necessary for peptic 

 digestion, in an acidity of 1-2 p. m. HC1, and further by the fact that the 

 proteins dissolve in trypsin digestion without previously swelling up. 

 As trypsin not only dissolves proteids, but also other protein sub- 

 stances such as gelatin, this latter body may be used in detecting tryp- 

 sin. The liquefaction of strongly disinfected gelatin is, according to 

 FERMi, 1 a very delicate test for trypsin or tryptic enzymes. Various 

 suggestions for the use of gelatin in the trypsin test have been made. 

 In consideration of the observations of ASCOLI and NEPPI that a trypsin 

 may not act upon fibrin or other proteids but still digest gelatin, it is 

 advisable never to make use of gelatin or proteid alone in testing for 

 trypsin, but always the two. 



For the quantitative estimation of trypsin by measuring the rapidity of 

 digestion we generally make use of the method of METT, described under pepsin 

 digestion. Another method, suggested by WEISS, consists in determining the 

 nitrogen in the filtrate after coagulation with heat and acetic acid. LOHLEIN 

 recommends the titration method of VOLHARD as used in pepsin determinations, 

 and has given directions for its use. JACOB Y recommends the use of ricin and 

 GROSS suggests a method based upon the precipitation of casein by acid. BAY- 

 LISS follows the digestion by the electrical conductivity, and HEDIN 2 determines 

 the quantity of nitrogen not precipitated by tannic acid. 



Many circumstances exert a marked influence on the rapidity of the 

 trypsin digestion. With an increase in the quantity of enzyme present 

 the digestion is hastened, at least to a certain point. According to 

 PAWLOW and his school, the rule of SCHUTZ-BORISSOW is perfectly applicable 

 to trypsin, and the amount digested is proportional to the square root 

 of the quantity of ferment. This does not agree with the results of 

 BAYLISS, HEDIN and others, making use of other methods of determina- 

 tion. HEDiN, 3 who has especially studied this question, found under cer- 

 tain conditions a direct proportion between the quantity of enzyme and 

 the intensity of digestion as explained in detail on pages 62, 63. Tryptic 

 digestion is also accelerated by an increase of temperature, at least to 

 about 40 C., at which temperature the protein is very rapidly dissolved 

 by the trypsin. The reaction is also of the greatest importance. Tryp- 

 sin acts energetically in neutral, or still better in alkaline, solutions, and 

 according to older statements, best in an alkalinity of 3-4 p. m. Na 2 CO 3 ; 



1 Arch. f. Hyg., 12 and 55. 



2 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; Hedin, ibid., 32. 



3 Pawlow, Die Arbeit der Verdauungsdriisen, Wiesbaden, 1898, p. 33; Bayliss, 1. c.; 

 Hedin, 1. c.; and Chapter II, pp. 62 and 63. 



