190 CHEMISTRY OF THE PROTEIDS CHAP. 



seems to be, however, no ferment present which dissociates albumin 

 hydrolytically, or which acts on the carboxyl-group of the amino-acids. 



The only reliable researches are those of Salaskin, 1 Salaskin and 

 Kowalewsky, 2 and Salaskin and Dzierzgowsky, 3 who worked with 

 gastric juice obtained by Pawlow's method. They also obtained 

 small amounts of ammonia, 3 leucinimide, 1 and amino-acids. Leu- 

 cinimide being readily formed from the peptid leucylleucin, could 

 therefore be accounted for. As regards the amino-acids, the objection 

 might be raised that they are formed from peptones owing to the 

 action of hydrochloric acid. Langstein 4 states that 1 per cent 

 sulphuric acid does not act on albumin even if it be allowed to act 

 for months ; but he did not determine its action on peptones, which, 

 according to Siegfried, 5 are very readily acted upon by acids. 



It is therefore questionable whether pepsin gives rise to amino- 

 acids : in any case only unappreciable amounts of these acids are 

 formed even after digesting for one to two months, for Salaskin 

 found that pepsin gave rise to only one -tenth the amount of 

 amino-acids which could be obtained by the action of mineral acids. 

 The large quantity of dissociation-products containing neither amino- 

 acids nor peptones, judging by the biuret-reaction, Pfaundler has shown 

 to be composed of substances intermediate between amino-acids and 

 peptones. He isolated an alcohol-soluble product which is precipitable 

 by mercuric sulphate but not by the alkaloidal reagents, and which 

 dissociates into leucin and a di-amino-acid, probably histidin, on being 

 treated with boiling hydrochloric acid. This substance is therefore a 

 compound of several arnino-acids, and occupies the same position as do 

 the synthetic peptids of E. Fischer (Chapter III.), and as does glycyl- 

 alanin, which E. Fischer and Bergell 6 prepared from the fibroin of silk 

 by a combined action of acids, trypsin, and alkali. Pfaundler says 

 justly, that the study of these products will give us the most important 

 information regarding the chemistry of albumins. Another similar 

 body is leucinimide, which Salaskin and Salaskin and Kowalewsky 

 found in peptic digests, and which consists of two molecules of leucin. 

 E. Fischer 7 and Abderhalden 8 believe it to be derived from leucyl- 

 leucin, i.e. a peptid. 



1 S. Salaskin, Zeitschr. f. physiol. Chem. 32. 592 (1901). 



2 S. Salaskin and K. Kowalewsky, ibid. 38. 567 (1903). 



3 S. Dzierzgowsky and S. Salaskin, Zentralbl.f. Physiol. 15. 249 (1901). 



4 L. Langsteiu, Zeitschr. f. physiol. Chem. 39. 208 (1903). 



6 M. Siegfried, Sitzungsber. d. sachs. Ges. d. Wissensch. zu Leipzig, 1903, p. 63. 



6 E. Fischer, Chemikerztg. 1902, II. p. 939. 



7 E. Fischer and E. Fourneau, Ber. d. deutsch. chem. Ges. 34. II. 2868 (1901). 



8 E. Abderhalden, Zeitsch'r.f. physiol. Chem. 37. 484 (1903). 



