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 diminish 
the amount of tissue proteid which is becoming broken down. This is 
also shown very conclusively in Yoit'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 Luciani, "Fisiol. d. digiuno," German translation, "Das Hunger," 1889; Richet, 
" L'inanition,"Travaux, 1893, tomeii. ; Tucsek, Centralbl. f. d.med. Wissensch., Berlin, 1885, 
S. 69 ; Lehmann, Mtiller, Senator, Zuntz, I. Munk, and others, Bcrl. klin. Wchnschr., 1887, 
S. 425 ; and Virchow's Archiv, 1893, Bd. cxxxi., Suppl.-Heft : I. Munk, Centralbl. f. d. 
med. Wissensch., Berlin, 1889, S. 833; Noel Paton and Stockman, Proe. Hoy. Soc. Edin., 
1889, p. 121 ; Praussnitz, Miinchen. med. Wchnschr., 1891, No. 18 ; and Ztschr. f. Biol., 
Miinchen, 1893, Bd. xi. S. 151 ; R. May, Hid., 1893, Bd. xii. S. 29 ; I. Munk, Arch. f. 
d. ges. Physiol., Bonn, 1894, Bd. lviii. S. 309 ; Johansson, Landgren, Sonden and 
Tigerstedt, Skandin. Arch. f. Physiol., Leipzig, 1896, Bd. vii. S. 29 ; C. Voit, Ztschr. 
f. Biol., Miinchen, 1894, Bd. xxx. S. 510 (comparison of weight of organs in well-nourished 
and starved dogs). See also on this subject, Lukjanow. Ztschr. f. physiol. C'hem., 
Strassburg, 1889, Bd. xiii. S. 339. 
2 Voit, op. cit. 
