528 DIGESTION. 



* 



peptone disappeared from the intestine, but that the blood passing 

 through did not contain any peptone. 



What becomes of the amino-acids in the intestinal wall? KUTSCHER 

 and SEEMANN have shown that the crystalline cleavage products are 

 so transformed in the intestinal wall that they cannot be detected. 

 We have here to think of two possibilities : The amino-acids are either 

 further split or they are used in synthesis (of proteins?). 



It is a long-known fact that with the digestion and absorption an 

 increased elimination of nitrogen in the urine goes hand in hand. The 

 quantity of nitrogen eliminated in the urine after partaking of protein 

 corresponded, according to ASHER and HAAS/ to 65 per cent of the 

 nitrogen introduced. It is hardly credible that this elimination of 

 nitrogen depends upon an increased destruction of body protein, and 

 it is more probable that this represents decomposed food-protein. 

 But according to NENCKI and ZALESKI 2 an abundant formation of 

 ammonia occurs in the cells of the digestive apparatus after a rich 

 protein diet, so we must consider the possibility that a considerable part, 

 perhaps the very greatest part, of the amino-acids are deamidized in 

 the intestinal wall. The other part of the amino-acids may be used 

 in the syntheses to be mentioned below. Such a partial deamidization 

 of the digestive products has been shown by COHNHEIM 3 in his absorp- 

 tion experiments with the fish intestine. 



The proteoses taken up by the intestinal mucosa, if this does take 

 place, can naturally undergo a further conversion into amino-acids in 

 the walls of the intestine. Still there are other possibilities. A direct 

 utilization of the proteoses in the synthesis of the proteins in the intes- 

 tine is not very probable, but on the contrary it is more probable that 

 the proteoses, in order to undergo further cleavage or further utiliza- 

 tion, are taken up by the leucocytes and carried off. HOFMEISTER 

 has advocated such a possibility for a long time. HEIDENHAIN raised 

 objections to this suggestion in which he called attention to the dis- 

 proportion between the number of leucocytes and the large quantity of 

 peptones (proteoses) to be absorbed, but at that time the deep cleavage 

 of a great part of the protein into amino-acids was not known. Recently 

 PRINGLE and CRAMER 4 urged the theory of the importance of the 

 leucocytes, and the observations of iNAGAKi 5 also show the possibility 



1 Bioch. Zeitschr., 12. 



2 Arch, des scienc. biol. de St. Pe"tersbourg, 4; Arch. f. exp. Path. u. Pharm., 37; 

 see also Salaskin, Zeitschr. f. Physiol. Chem., 25. 



1 Zeitschr. f . physiol. Chem., 59. 



4 Hofmeister, 1. c.; Heidenhain, Pfluger's Arch., 43; Pringle and Cramer, Journ. 

 of Physiol., 37. 



6 Zeitschr. f. physiol. Chem., 50. 



