ACTION OF TRYPSIN. 505 



this enzyme glutinase. This glutinase is much more resistant toward acids 

 than trypsin, and by proper treatment with acids POLLAK was able to change a 

 pancreas infusion so that it acted upon gelatin and not upon certain proteins. 

 The correctness of these observations has, indeed, not been generally accepted, 

 and it is disputed by ASCOLI and NEPPi. 1 According to them the action of the 

 trypsin is weakened by the acid, and indeed to such varying degrees for differ- 

 ent proteins that the action upon albumin is lost while the action upon gelatin 

 is noticeable. Nevertheless, we here have a warning to be careful as to the 

 conclusions drawn from results where impure infusions are used. For many 

 experiments it is undoubtedly advisable to use the natural pancreatic juice. 



The following reports on the action of trypsin applies to the so- 

 called trypsin, with the reservation that it is perhaps not a unit enzyme. 



The action of trypsin on proteins is best demonstrated by the use of 

 fibrin. Very considerable quantities of this protein body are dissolved 

 by a small amount of trypsin at 37-40 C. It is always necessary to 

 make a control test with fibrin alone, with or without the addition of 

 alkali. Fibrin is dissolved by trypsin without any putrefaction; the 

 liquid has a pleasant odor somewhat like bouillon. To completely 

 exclude putrefaction a little thymol, chloroform, or toluene should be 

 added to the liquid. Tryptic digestion differs essentially from peptic 

 digestion, irrespective of the difference in the digestive products, in that 

 the first takes place in neutral or alkaline reaction and not, as is neces- 

 sary 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 pre- 

 viously 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, 2 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 nitrate 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- 



1 Pollak, Hofmeister's Beitrage, 6; contradictory statements are found in Ehren- 

 reich, cited in Bioch. Centralbl., 4; Ascoli and Neppi, Zeitschr. f. physiol. Chem., 56. 



2 Arch, f . Hyg. 12 and 55. 



