68 PROTEIN DIGESTION IN THE INTESTINE 



practical interest in agriculture, an unusually large number 

 of studies have been directed to the question of how far 

 amides, especially as par agin (as W. Voltz and others have 

 maintained), are capable of replacing the protein of food. 56 

 It is readily appreciable that amides and aminoacids may 

 serve as conservers of protein. There is, however, a con- 

 stantly recurring idea that at least in herbivora protein may 

 be replaced by such amides. N. Zuntz, 0. Hagemann and 

 other writers would find the key to the whole problem in the 

 role of the intestinal bacteria. Introduction of asparagin 

 and similar substances they believe not only serves to con- 

 serve protein and preserve the dietary protein from the influ- 

 ence of the bacteria; but the amides are a medium from 

 which the bacteria because of their plant characteristics are 

 able to construct protein. If in the end the bacteria die, this 

 protein of theirs is of advantage to the vertebrate animal. 

 In this manner not only asparagin, but ammonium acetate 

 and many other ammonium salts may indirectly, of course, 

 become a source of protein for the animal body. In the 

 course of the last few months the question of the availability 

 of ammonium salts and amides to enter into protein synthesis 

 has been brought into prominence from the studies of 

 E. Graf e and of Abderhalden. 



E. Graf e and Schlapf er from extensive metabolic studies 

 determined that in dogs receiving a full diet of non- 

 nitrogenous material not only nitrogen balance but actual 

 nitrogen retention and increase of weight can be obtained by 

 feeding ammonium citrate, without subsequent outpouring 



66 K. Anderlik, K. Velich and VI. Stanek, K. Friedlander, S. Gabriel, O. 

 Hagemann, V. Henriques and C. Hansen, J. Just, O. Kellner, C. Lehman, 

 A. Morgen, C. Beger and F. Westliauser, Mauthner, M. Mtiller, J. Munck, E. 

 Peschek, G. Politis, B. v. Strusiewicz, F. Rosenfeld, W. Thar, W. Voltz, H. 

 Weiske, N. Zunz. Literature: H. Liithje, Ergebn. d. Physiol., 7, 828-830, 

 1908; E. Abderhalden, Vorlesungen, 2d ed., pp. 301-303, 1909; P. Rona, Handb. 

 d. Biochem., 4', 554-559, 1911; E. Peschek (Zootech Instit. of Agricul. School, 

 Berlin), Pfliiger's Arch., 142, 143, 1911. 



