876 METABOLISM. 
Klemperer l reduced the amount of proteid in his own diet to as little as 
25 grms. per diem, hut required 262 grms. fat, and 406 grrns. carbohydrate 
(with a total caloric value of more than 5,000,000 calories) to maintain 
equilibrium. 
I. ]\Iunk brought a dog into nitrogenous equilibrium with a diet con- 
sisting mainly of proteid. If, now, one -half the proteid of the diet was 
removed and replaced by non-proteid, an amount of non-proteid having a 
caloric value of about two-fifths more than that of the proteid removed was 
required to maintain equilibrium ; and the more the proteid removed from the 
diet, the greater the proportionate amount of non-proteid required. Ultimately, 
the amount of proteid was reduced to 1-5 grms. per kilo, body-weight; under 
these circumstances an amount of non-proteid, twelve to fifteen times the 
caloric value of the proteid removed, was reqiured to maintain equilibrium. 2 
After the lapse of some weeks, the animal failed properly to digest the large 
amount of non-proteid required, and it became necessary to reduce this and 
increase the proteid. 
The amount of nitrogen taken in these experiments was distinctly less 
than the amount which would be lost in the fasting condition. 
Of the two chief kinds of non-proteid food, v. Xoorden and Ivayser 3 have 
found that carbohydrates are of greater value as proteid-sparers than fats. In 
a mixed diet, therefore, containing just enough proteid and non-proteid for 
the needs of the economy, fats cannot be substituted for their caloric 
equivalent of carbohydrates without loss of proteid occurring. Gelatin is of 
still greater value as a proteid-sparing food than are either fats or carbohydrates 
(see p. 878), and by its use, although it cannot be built up into tissue, the 
amount of tissue proteid lost from the body can be reduced, according to Voit, 
to about the half of that which is normally lost, and which on Voit's estimate 
amounts to about 33 grms. daily, 4 or 1 per cent, of the actual living substance. 5 
The importance of gelatin as an article of diet will be specially treated of 
later on. 6 
In spite of such experiments, it may be doubted whether a diet which 
includes considerably less proteid than 100 grms. for the twenty-four 
hours could maintain a man of average size and weight for an indefinite 
time. It has frequently been asserted that many Asiatics consume a 
very much smaller proportion of proteid than is the case with Europeans. 
The inhabitants of India, Japan, and China chiefly consume rice as the 
normal constitution of their diet, which contains relatively little proteid ; 
and this has been advanced as an argument in favour of the view that 
the minimal amount of proteid is much less than that ordinarily given 
as essential to the maintenance of nutritive equilibrium. It must, 
however, be stated that we have no definite statistics to show that, in 
1 Arch. f. Physiol., Leipzig, 1889, S. 361. Similar experiments have been made by 
Peschel (Diss., Berlin, 1890) and Graham Lusk, Ztschr. f. Biol, Miinchen, 1891, Bd. xxvii. 
S. 459. See also E. Voit. Miinchen. med. Wchnsehr., 1889, S. 748 ; and C. Voit, ibid., 
1891, S. 195. 
2 Arch. f. Physiol., Leipzig, 1891, S. 338 {Verhandl. d. physiol. Gesellsch.) and 
Vlrchoic's Archiv, 1893, Bd. cxxxii. S. 91. See also Rosenheim, Arch. f. d. ges. Physiol., 
Bonn, 1893, Bd. liv. S. 61 ; and Ritter, Miinchen. med. Wchnsehr., 1893, Nos. 31 and 32. 
3 Arch. f. Physiol., Leipzig, 1893, S. 371. 
4 The half of this amount, since it can be replaced by gelatin, is set down by Voit to 
disintegration of "circulating proteid" instead of actual "tissue proteid." 
5 Hermann's "Handbuch," Bd. vi. S. 302. and Ztschr. f. Biol, Miinchen, 1S89. Bd. 
vii. S. 2S4. 
u Pagliese, Ccntralbl. f. Physiol, Leipzig u. Wien, 1897, S. 329, has found that fats, 
carbohydrates, and gelatin, not only diminish the amount of the nitrogen excreted, but 
also the phosphoric acid, and this even in a greater proportion, and probably by diminish- 
ing the waste of the nucleo-proteids of the tissues. 
