v PLASTEINS AND PEPTONES 193 



Plastein in the alcohol-acetone solution differs greatly from other 

 albumins, for on analysis it yielded these percentages 



C 38-43 H 7-01 N 8'05 



Bayer obtained no plastein on adding rennet-ferment (' pegnin ' of the 

 Hochst Manufactory) to pro to-, hetero-, thio-, and gluco-albumoses, pre- 

 pared from Witte's peptone according to Pick's method. (See p. 179.) 

 Kiihne l has observed that hetero-albumose has a great tendency to 

 become insoluble on being kept, or by being heated up to 55. This 

 insoluble form of hetero-albumose Kiihne termed ' dys-albumose.' In 

 all probability plastein and anti-albumid are one and the same body, 

 and closely related to dys-albumose. We do not yet know whether 

 the formation of this insoluble body depends on rennin, on salts, or 

 on some other factor. The amount of the precipitate depends on the 

 strength of the ferment, as active pepsin, e.g. pure gastric juice, 

 dissolves the precipitate : it was obtained in largest amount if by 

 adding ammonium sulphate the action of pepsin was interfered with. 

 Rotarski's 2 statement that the anti-albumid coagulum can only be 

 obtained from albumin which has been altered by heat is incorrect, as 

 Umber obtained it also from raw egg-white. On being still further 

 digested, anti-albumid yields the products of the anti-group ; it is, how- 

 ever, unsuitable for preparing anti-peptone, for it yields only small 

 quantities, according to Siegfried and Miiller. 3 



II. THE PEPTONES FORMED BY TRYPTIC DIGESTION 



Claude Bernard and Corvisart were the first to discover that 

 pancreatic juice dissolves and dissociates proteids. Kiihne 4 showed 

 subsequently that this dissociation is a very pronounced one, as it leads 

 to the formation of the same crystalline products as are obtained 

 by acting on albumins with boiling mineral acids. He also showed 

 that the pancreatic action depends on the presence of the ferment 

 trypsin, which acts in alkaline, neutral, or acid, but best in feebly 

 alkaline solutions. 5 Kiihne discovered leucin, tyrosin, and ' trypto- 

 phane'; Salkowski and Radziejewski, 6 Knieriem, 7 Hirschler, 8 Stadel- 



1 W. Kiihne and R. H. Chittenden, Zeitschr.f. Biol. 2O. 11 (1884). 



2 T. Rotarski, Zeitschr. f. physiol. Ghem. 38. 552 (1903). 

 :! F. Miiller, ibid. 38. 265 (1903). 



4 W. Kiihne, Virchow's Arch. 39. 130 (1867) ; Verh. d. Heidelberger nat.-med. 

 Vereins, N.F. I. 236, III. 463 (1886). 



5 W. Kiihne, Verh. d. Heidelberger naturh.-med. Vereins, N.F. I. 190 (1876) ; A. 

 Dietze, Medizinische Dissertation, Leipzig, 1900. 



6 E. Salkowski and S. Radziejewski, Ber. d. deutsch. chem. Oes. 7. II. 1050 (1874). 



7 Kuieriem, Zeitschr.f. Biol. 11. 199 (1875). 



8 A. Hirschler, Zeitschr. f. physiol. Chem. 10. 302 (1886). 







