480 DIGESTION. 



kingdom, 1 in yeast and in higher plants, and are also formed by various 

 bacteria. The enzymes similar to trypsin occurring in the plant king- 

 dom are, according to VINES, a mixture of peptases, which transform the 

 proteins into peptone and ireptases, which split the peptones into amino- 

 acids. 



As we know of so-called antienzymes for other enzymes, so we also have anti- 

 trypsins, and not only in the intestinal canal but also in the blood-serum. The 

 results as to the specificity of these antitrypsins in various animals, as well as 

 the possibility of producing antitrypsins by immunization, is still disputed. 



.Trypsin, like other enzymes, has not been prepared in a pure condi- 

 tion. Nothing is positively known in regard to its nature, but as obtained 

 thus far it shows a variable behavior (KtJHNE, KLUG, LEVENE, MAYS, 

 and others) . At least it does not seem to be a nucleoprotein, and trypsin 

 has also been obtained which did not give the biuret test (KLUG, MAYS, 

 SCHWARZCHILD) . Trypsin dissolves in water and glycerin, while KUHNE'S- 

 trypsin is insoluble in glycerin. It is very sensitive to heat, and even 

 the body temperature gradually decomposes it (VERNON, MAYS). In 

 neutral solution it becomes inactive at 45 C. In dilute soda solution 

 of 3-5 p. m. it is still more readily destroyed (BIERNACKI, VERNON 2 ). 

 The presence of protein or proteoses has, to a certain extent, a pro- 

 tective action on heating an alkaline trypsin solution, and this has been 

 substantiated by recent investigations of BAYLISS and VERNON. The 

 simpler cleavage products have a still greater protective action (VERNON 3 ) . 

 Trypsinogen, according to the unanimous statements of several exper- 

 imenters, is more resistant toward alkalies than trypsin. Tiypsin is 

 gradually destroyed by gastric juice and even by digestive hydrochloric 

 acid alone. 



The preparation of pure trypsin has been tried by various experimenters. 

 The most careful work in this direction was done by KUHNE and MAYS. 

 Various methods have been suggested by MAYS, but we cannot enter into 

 a discussion of them. A very pure preparation can be obtained by mak- 

 ing use of the combined salting out with NaCl and MgSO 4 . A very active 

 solution, and one that can be kept for a long time (for more than twenty 

 years according to HAMMARSTEN), can be obtained by extracting with 

 glycerin (HEIDENHAIN 4 ) . An impure but still very active infusion 



1 In this connection see Vines, Annals of Botany, 16, 17, 18, 19, 22, and 23, and 

 Oppenheimer, Die Fennente, 1900. 



3 Kiihne, Verb. d. naturh.-med. Vereins zu Heidelberg (N. F.), 1, 3; Klug, Math, 

 naturw. Ber. aus Ungarn., 18, 1902; Levene, Amer. Journ. of PhysioL, 5; Mays, 

 Zeitschr. f. Physiol. Chem., 38; Vernon, Journ. of Physiol., 28 and 29; Biernacki, 

 Zeitschr. f. Biologic, 28; Schwarzschild, Hofmeister's Beitrage, 4. 



3 Bayliss, Arch, des scienc. biolog. de St. Petersbourg, 11, Suppl.; Vernon, Journ. 

 of Physiol., 31. 



4 Pfliiger's Arch., 10. 



