PROTEOSES, ASPARAGIN, MIXED DIETS. 855 



they can spare the proteins, but cannot be converted into proteins. 

 According to the researches of BLUM the different proteoses have various 

 nutritive values. In his experiments the heteroproteose from fibrin 

 could not replace the proteins of the food, while casein protoproteose 

 had this property. In the researches of HENRIQUES and HANSEN 1 

 on white mice it was shown that the heteroproteose as well as the dys- 

 proteose (from WITTE peptone) had the ability of protecting the body 

 from loss of nitrogen and that they deposited nitrogen. If the animal 

 body has the ability of again constructing protein from simple fractions 

 then there is nothing strange in these reports on the nutritive value of 

 proteoses. The proteoses and peptones are formed by cleavages, and 

 perhaps certain atomic complexes are absent which occur in the mixture 

 of cleavage products and which are necessary for a regeneration of special 

 protein bodies. 



We have a number of investigations on the action of amides upon 

 metabolism, which are mostly connected by the use of asparagin. These 

 investigations have in part led to conflicting results; but they indicate 

 that carnivora and herbivora act differently, that the results are 

 dependent upon the rapidity with which the asparagin is absorbed 

 and also upon the bacterial action in the intestine, and that in herbivora 

 a protein-sparing action can be brought about by asparagin. 2 If, as is 

 generally admitted, the amino-acids can serve in the building up of the 

 proteins, then there is no use denying that their amides can also be used 

 by the animal body. The most important facts in connection with the 

 relation of the amino-acids to the protein metabolism and protein syn-* 

 theses have been mentioned in a previous Chapter (IX). 



Metabolism on a Diet consisting of Protein, with Fat or Carbohydrates. 

 Fat cannot arrest or prevent the catabolism of proteins; but it can decrease 

 it, and so spare the proteins. This is apparent from the following table 

 of VoiT. 3 A is the average for three days, and B for six days. 



Food. Flesh. 



Meat. Fat. Metabolized. On the Body. 



A 1500 1512 -12 



B 1500 150 1474 +26 



1 Blum, Zeitschr. f. physiol. Chem., 30; Voit, 1. c., 394; Henriques and Hansen, 

 Zeitschr. f. physiol. Chem., 48. 



2 Weiske, Zeitschr. f . Biologic, 15 and 17, and Centralbl. f. d. med. Wissensch., 1890, 

 945: Munk, Virchow's Arch., 94 and 98; Politis, Zeitschr. f. Biologic, 28. See also 

 Mauthner, ibid., 28; Gabriel, ibid., 29; and Voit, ibid., 29, 125; Kellner, Maly's Jahres- 

 ber., 27, and Zeitschr. f. Biologic, 39; Pfliiger's Arch., 113; Kellner and Kohter, Chem. 

 Centralbl., 1, 1906. Voltz, Pfliiger's Arch., 107, 117, with Yakuwa, ibid., 121; v. 

 Strusiewicz, Zeitschr. f. Biol., 47; Rosenfeld and Lehmann, Pfliiger's Arch., 112; 

 Lehmann, ibid., 115; M. Midler, ibid., 117; Henriques and Hansen, Zeitschr. f. physiol. 

 Chem., 54. 



3 Voit in Hermann's Handbuch, 6, 130. 



