416 PRINCIPLES OF ANIMAL NUTRITION, 
To the above results we may add those of Magnus-Levy’s deter- 
minations (p. 381) of the work of digestion and assimilation in the 
dog on a meat diet as follows: 
Metabolizable Expended in Net Available. 
Proteids Eaten, Energy of Digestion and 
Grms. Food, Assimilation, 
Cals. Cals. Total Per Cent. 
82.5 338 56 282 83.43 
230.0 943 116 827 87.70 
370.6* 1520 244 1276 83.95 
* In excess of maintenance requirements. 
The wide range of the results obtained by Rubner would seem to 
indicate either that the net availability of the energy of the pro- 
teids may vary with different animals and under different conditions 
or that the experimental methods were not sufficiently sharp for the 
purpose now in view. The value of an average drawn from such 
results is questionable, but for the sake of comparison it is included 
below along with those derived from Voit’s and Magnus-Levy’s 
experiments, Voit’s first result being omitted because impossible. 
The figures express the average net availability as a percentage 
of the metabolizable energy. 
Voit’s experiments ............... 85.60 per cent. 
Rubner’s experiments ............ 82.80 “ “ 
Magnus-Levy’s experiments......... 85.03 “ = “ 
Fat.—Computing the results obtained by Pettenkofer & Voit * 
and by Rubner 7 upon the effects of fat on the total metabolism 
(see pp. 144-146) in the same manner as those upon the proteids, 
and adding Magnus-Levy’s results (p. 379), we have the table 
opposite. 
Rubner’s and Magnus-Levy’s results do not differ widely, and 
their average, 96.4 per cent., indicates a relatively small expendi- 
ture of energy in the digestion and assimilation of fat, which does 
not appear to materially increase above the maintenance require- 
ment. Most of Pettenkofer & Voit’s experiments give materially 
lower results above that point, and the one case in which the food 
* Zeit. f. Biol., 5, 370; 7, 440-443; 9, 3-13. 
ft Ibid., 19, 328-334; 30, 123. 
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