876 METABOLISM. 



Klemperer 1 reduced the amount of proteid in his own diet to as little as 

 25 grms. per diem, but required 262 grins, fat, and 406 grms. carbohydrate 

 (with a total caloric value of more than 5,000,000 calories) to maintain 

 equilibrium. 



I. Munk 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-pro teid, an amount of non-pro teid 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 T5 grms. per kilo, body-weight; under 

 these circumstances an amount of non-proteid, twelve to fifteen times the 

 caloric value of the proteid removed, wlls required 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. Noorden and Kayser 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 Yoit, 

 to about the half of that which is normally lost, and which on Voit's estimate 

 amounts to about 33 grins, 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 Lnsk, Ztschr. f. Biol., Miinchen, 1891, Bd. xxvii. 

 S. 459. See also E. Voit, Miinchen. med. Wchnschr., 1889, S. 748 ; and C. Voit, ibid., 

 1891, S. 195. 



* Arch. f. Physiol., Leipzig, 1891, S. 338 (Verliandl. d. physiol. Gesellsch.) and 

 Virchow'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. Wchnschr., 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 /Aschr. f. Biol., Miinchen, 1889, Bd. 

 vii. S. 284. 



6 Pagliese, Centralbl. f. Physiol., Leipzig u. Wicn, 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. 



