PROTEOSES AND PEPTONES. 131 



The older view that in peptic digestion only proteoses and peptones, 

 but no simpler cleavage products, are formed, has been shown not to be 

 true. The works of ZUNZ, PFAUNDLER, SALASKIN, LAWROW, LANGSTEIN,* 

 and others have shown that by very lengthy digestion simpler products 

 can be produced, some whose nature is still unknown, while others are 

 known, such as alanine, leucine, leucinimide, valine, aspartic and glutamic 

 acids, phenylalanine, tyrosine, proline and lysine, and on further cleavage 

 indeed also oxyphenylethylamine, tetra- and pentamethylenediamine. 

 It has not been possible to cause a disappearance of the biuret reaction, 

 and the occurrence of tryptophane is somewhat disputed. MALFATTI 

 obtained tryptophane in peptic digestion only when he used a certain 

 apparently impure preparation of pepsin, and on using pepsin purified 

 according to PEKELHARING it was absent. According to PEKELHARiNG, 2 

 purified pepsin also yields tryptophane when the solution is rich in pep- 

 sin, and also when the acidity is not too strong, in the presence of small 

 amounts of pepsin. 



In connection with the above-mentioned experimental results it must be 

 remarked that not all the products found, for example the oxyphenylethylamine 

 and the diamines, are produced by the action of pepsin, but rather by the action of 

 other enzymes. In certain cases, undoubtedly, impure pepsin was used, or indeed 

 autodigestion of the stomach was carried on, and the action of other enzymes 

 was not excluded. In other cases the digestion with pepsin and considerable 

 acid (even 1 per cent HzSOJ was continued for a very long time, indeed for an 

 entire year, without controlling the influence of the acid alone upon the proteoses. 

 The question as to the hydrolysis with the splitting off of amino-acids by the 

 continuous action of acid alone is still the subject of dispute. 



KUHNE'S view that in tryptic digestion a peptone, so-called antipep- 

 tone, always remains which cannot be further split is not strictly true. 

 By sufficiently long autodigestion of the pancreas, KUTSCHER 3 was able 

 to obtain, as final products, a mixture of digestion products which failed to 

 respond to the biuret test, and the same results have been obtained by 

 others. In this connection we must remark that the. pure antipeptone 

 (see below), isolated by SIEGFRIED, could be split by trypsin only with 

 great difficulty, and also that the complete disappearance of the biuret 

 reaction in tryptic digestion does not show that a complete decomposi- 

 tion into amino-acids has taken place. According to E. FISCHER and 

 AfiDERHALDEN, 4 polypeptide-like bodies are produced, especially in 



1 Zunz, Zeitschr. f. physiol. Chem., 28, and Hofmeister's Beitrage, 2; Pfaundler, 

 Zeitschr. f. physiol. Chem., 30; Salaskin. ibid., 32; Salaskin and Kowalewsky, ibid., 

 38; Lawrow. ibid., 33; Langstein, Hofmeister's Beitrage, 1 and 2. 



2 Malfatti, Zeitschr. f. physiol. Chem., 31; Pekelharing, Archives d. scienc. biolog. 

 de St. Pe"tersbourg, 11; Pawlow Festband. 



3 Zeitschr. f. physiol. Chem., 25, 26, 28, and Die Endprodukte der Trypsinver^ 

 darning, Habilitationsschrift Strassburg, 1899. 



4 Zeitschr. f. physiol. Chem., 39. 



