854 METABOLISM. 



himself with 93 per cent gelatin nitrogen, 4 per cent tyrosine nitrogen, 

 2 per cent cystin nitrogen, and 1 per cent tryptophane nitrogen, he found 

 instead of the equal quantity of protein nitrogen in the periods before 

 and after, that the gelatin replaced by amino acids had almost the same 

 physiological value as the proteins. The correctness of this action of the 

 amino-acids has unfortunately not been confirmed by others. RONA and 

 MiCHAELis, 1 who also proved that one-fifth of the protein metabolism 

 could be replaced by gelatin, found that no mentionable increase in the 

 the nutritive value of gelatin on the addition of tyrosin or tryptophane 

 occurred. 



The value of gelatin has been found by MURLIN 2 to be dependent to 

 a high degree upon the protein condition ot the body, on the calorific 

 value of the food and the quantity of carbohydrates in the latter. If 

 in a man weighing 70 kilos, 51 calories per kilo were partaken, the quan- 

 tity of nitrogen eliminated was 10 per cent more than the starvation 

 value, and when two-thirds of the total calories partaken of were 

 supplied by carbohydrates, 63 per cent of the total nitrogen could be 

 replaced by gelatin nitrogen. 



Gelatin may also somewhat decrease the consumption of fat, although 

 it is of less value in this respect than the carbohydrates. 



The nutritive value of proteoses (and peptones) stands in close 

 relation to the nutritive value of the proteins and gelatin. The early 

 investigations made by MALY, PLOSZ and GYERGYAY, and ADAMKIEWICZ 

 have led to the conclusion that with food which contains no proteins 

 besides peptones (proteoses) an animal may not only preserve its nitrog- 

 enous equilibrium, but its protein condition may even increase. 

 According to recent and more exact investigations by POLLITZER, ZUNTZ, 

 and MUNK the proteoses have the same nutritive value as proteins, at 

 least in short experiments. POLLITZER claims that this is true for dif- 

 ferent proteoses as well as for true peptone; but this does not agree 

 with the experience of ELLINGER, S who finds that the true antipeptone 

 (gland peptone) is not able to replace proteins entirely or to prevent 

 the loss of protein in the animal body. On the contrary, he claims 

 it has, like gelatin, the property of sparing proteins. VOIT long ago 

 expressed a similar view. He believes that the proteoses and peptones 

 may indeed replace the proteins for a short time, but not permanently; 



1 Krummacher, Zeitschr. f. Biologie, 42; Kirchmann, ibid., 40; Kaufmann, Pfliiger's 

 Arch., 109; Rona and Michaelis, Zeitschr. f. physiol. Chem., 50. 



2 Amer. Journ. of Physiol., 19. 



3 Maly, Pfliiger's Arch., 9; Plosz and Gyergyay, ibid., 10; Adamkiewicz, " Die Natur 

 und der Nahrwerth des Peptons " (Berlin, 1877); Pollitzer, Pfliiger's Arch., 37, 301; 

 Zuntz, ibid., 37, 313; Munk, Centralbl. f. d. med. Wissensch., 1889, 20, and Deutsch. 

 med. Wochenschr., 1889; Ellinger, Zeitschr. f. Biologie, 33 (literature). 



