SYNTHESIS OF THE PRODUCTS OF DIGESTION 61 



Kutscher and Seemaim 39 have determined that rela- 

 tively simple abiuret substances are included in the ex- 

 tractives of the intestine, which split when treated with boil- 

 ing mineral acids with the production of leucin in consider- 

 able amounts. This observation may perhaps have some bear- 

 ing upon the possibility of the leucin from the intestinal 

 mucous membrane (and of many other simple products of 

 protein cleavage) having previously undergone a process of 

 coupling directly in the intestinal wall. Bearing upon con- 

 densation processes, the extensive observations of Danilew- 

 ski and his students (vide supra,, p. 30) upon plastein 

 formation should be noted. In albumose solutions autolysed 

 with intestinal mucous membrane an increase of coagulable 

 nitrogen at the expense of incoagulable nitrogen has been 

 found, 40 interpreted tentatively as transformation of 

 albumoses into serum albumin. A mixture of the digestion- 

 products of casein has been observed to "jell" under the 

 influence of intestinal secretion supposedly due to the action 

 of a ferment. 41 Ernst Freund observed that upon bringing 

 together fresh horse-serum and a solution of Witte's pep- 

 tone a portion of the albumoses become coagulable, and, 

 further, that of the serum-proteins only euglobulin shows 

 this characteristic, and that after addition of the peptone to 

 serum the euglobulin fraction diminishes, while the pseudo- 

 globulin and albumin fractions increase. 42 Italian authors 

 have stated that precipitates are given by various tissue ex- 

 tracts, some with blood-serum, some with peptone; and have 

 suggested the former type of precipitation as an expression 

 of a binding of the circulating dietary protein with the 

 tissue proteins. 43 



89 F. Kutscher and J. Seemann (Physiol. Instit., Marburg), Zeitsch. f. 

 physiol. Chem., 85, 432, 1902. 



^Grosmann (Kurajeff's Lab., Charkow), Hofmeister's Beitr., 6, 192, 1905. 



41 E. S. London, Zeitschr. f. physiol. Chem., 74, 301, 1911. 



48 E. Freund, Wiener med. Wochenschr., 1905, No. 47; 1909, 108. 



43 Pacchioni and Carlini (Pediatric Clinic, Florence), Arch, di Fisiol., 2, 

 297, 1905; abstract, Biochem. Centralbl., 4, 1490, 1905-06. 



