NUTRITION WITH A PURELY PROTEID DIET. 891 



The literature of the subject, since the article by Voit in Hermann's 

 " Handbuch " (1881), will be found mainly in the memoirs noted below. 1 



NUTRITION WITH A PURELY PROTEID DIET. 



Under the circumstances we have been considering, namely, complete 

 deprivation of food, the nitrogen excreted must come from the nitrogen 

 of the tissues, and it might be supposed that if we supply a starving 

 animal with food containing the exact amount of nitrogen (in the form 

 of proteid) which it is losing, we should be able to entirely prevent such 

 waste of the tissues, and that any loss then occurring would arise solely 

 from non-proteid substances. This, however, is not the case. For if 

 this experiment is performed, it is found that the animal loses more 

 nitrogen than we give it. The whole of the nitrogen of the added 

 proteid appears in the urine as urea, and in addition there is a certain 

 amount, although not as much as during complete starvation, of tissue 

 nitrogen still present in the urine. In order to keep up nitrogenous 

 equilibrium, Voit found that it was necessary to give two and a half 

 times as much proteid as the animal had metabolised during fasting. 

 This result, which is at first sight somewhat unexpected, is due to the 

 fact that the ingestion of proteid food directly excites the tissues to 

 increased metabolic activity, so that tissue proteid itself still becomes 

 split up and oxidised. 



How and why the activity of the living tissues is thus stimulated 

 by increased proteid pabulum is a problem as to which we are entirely 

 in the dark. Non-proteid substances do not produce this effect. On the 

 contrary, the giving of gelatin, carbohydrates, and fat has, as we have 

 seen, a sparing effect upon proteid metabolism, and tends to dimmish 

 the amount of tissue proteid which is becoming broken down. This is 

 also shown very conclusively in Voit's experiments on dogs which had 

 been kept in a condition of N-equilibrium with proteid food. The con- 

 dition of N-equilibrium could be produced with a far smaller amount 

 of proteid, provided that for the amount removed an adequate quantity 

 of fat or carbohydrate was added to the diet. 2 



If to a starving animal, instead of what would appear to be just a 

 sufficient amount of proteid, an excess be given, a point is at length 

 reached at which the building-up process exceeds the breaking-down, 

 and the tissues, and therefore the body generally, gain in weight. 

 This increase in body weight, due to the laying on of tissue, proceeds 

 to a certain point with any constant amount of added proteid, until 

 a balance between the N laid on and the N lost is struck, when a 

 condition of N-equilibrium is again obtained. A further increase of 



1 Lnciani, "Fisiol. d. digiuno," German translation, "Das Hunger," 1889; Richet, 

 " L'inanition," Travaux, 1893, tome ii. ; Tucsek, Centralbl. f. d. med. Wissensch. , Berlin, 1 885, 

 S. 69 ; Lehmann, M tiller, Senator, Zuntz, I. Munk, and others, Berl. klin. Wchnschr., 1887, 

 S. 425 ; and Virchoivs Archiv, 1893, Bd. cxxxi., Suppl.-Heft; I. Munk, Centralbl. f. d. 

 med. Wissensch., Berlin, 1889, S. 833; Noel Paton and Stockman, Proc. Roy. Soc. Edin., 

 1889, p. 121 ; Praussnitz, Munchen. med. Wchnschr., 1891, No. 18 ; and Ztschr. f. BioL, 

 Mtinchen, 1893, Bd. xi. S. 151 ; R. May, ibid., 1893, Bd. xii. S. 29 ; I. Munk, Arch. f. 

 d. ges. Physiol., Bonn, 1894, Bd. Iviii. S. 309 ; Johansson, Landgren, Sonden and 

 Tigerstedt, Skandin. Arch. f. PhysioL, Leipzig, 1896, Bd. vii. S. 29 ; C. Voit, Ztschr. 

 f. Biol., Munchen, 1894,. Bd. xxx. S. 510 (comparison of weight of organs in well-nourished 

 and starved dogs). See also on this subject, LukjanoAV. Ztschr. f. physiol. Chem., 

 Strasslmrg, 1889, Bd. xiii. S. 339. 



2 Voit, op. cit. 



