v PEPTONES AND PEPTIDS 189 



which gave Millon's but not Molisch's reaction. Frankel and 

 Langstein l have broken up pepsin-peptone into four fractions. 



Peptids 



Kiihne had assumed that peptic digestion only proceeded to the 

 formation of peptone, but Zunz, 2 Pick, 3 Pfaundler, 4 and Reach 5 showed, 

 after precipitating the albumoses and peptones, even if digestion had 

 been going on for only a short time, that over one-half of the nitrogen 

 was in solution in some non-proteid form, i.e. a form which did not 

 give the biuret-reaction. It might have been thought that pepsin 

 acted similarly to trypsin, but only more slowly, and that it also gave 

 rise to amino-acids, and therefore a large number of attempts have 

 been made to find amino-acids after very prolonged peptic digestion. 

 The older experiments of Lubavin, 6 Mohlenfeld, 7 Lawrow, 8 and 

 Langstein 9 did not settle this question ; for they were made with the 

 gastric mucous membrane, and we know through Salkowski, 10 Jacoby, 11 

 and Vernon 12 that all organs contain small amounts of ferments capable 

 of dissociating albumins into amino-acids and even into more simple 

 compounds. In purifying pepsin, the albumins and salts are got rid 

 of ; but traces of the ferments just alluded to are not removed, because 

 they have the same solubility as pepsin. That tryptic ferments are 

 present has been shown by Malfatti 13 and Zunz, 14 and the ' pseudo- 

 pepsin,' the non-existence of which Klug 15 and Pawlow 16 have since 

 proved, is probably, also a trypsin-like body. That besides pepsin other 

 ferments are also present is proved by the researches of Langstein and 

 Lawrow, who find phenylethylamin, putrescin, and cadaverin. There 



1 S. Frankel and L. Langstein, Sitzungsber. d. Wiener Akad., math.-iiat. Kl. 110. 

 Abt. II 6 . February 1901. 



2 E. Zunz, Zeitschr. f. physiol. Chem. 28. 132 (1899) ; Hofmeister's Beitrage, 2. 

 435 (1902), 3. 339 (1902). 



3 E. P. Pick, Zeitschr. f. physiol. Chem. 28. 219 (1899). 



4 M. Pfaundler, ibid. 30. 90 (1900). 



5 F. Reach, Hofmeister's Beitrage, 4. 139 (1903). 



6 Lubavin, Hoppe-Seyler's med.-chem. Untersuch. p. 463 (1871). 



7 Mohlenfeld, Pfliigers Arch. 5. 381 (1872). 



8 D. Lawrow, Zeitschr. f. physiol. Chem. 26. 513 (1899), 33. 312 (1901). 



9 L. Langstein, Hofmeister's Beitrage, 1. 507 (1902), 2. 229 (1902). 



10 E. Salkowski, Zeitschr. f. Tdin. Medizin, 1891, Suppl. 



11 M. Jacoby, Zeitschr. f. physiol. Chem. SO. 149 (1900). 



12 H. M. Vernon, Journ. of Physiol. 32. 33 (1904). 



13 H. Malfatti, ibid. 31. 43 (1900). 



14 E. Zunz, Hofmeister's Beitrage, 2. 435 (1902). 



15 F. Klug, Pfluger's Arch. 92. 281 (1902). 



1(i S. Salaskin and K. Kowalewsky, Zeitschr. f. physiol. Chem. 38. 571 (1903). 



