104 PRINCIPLES OF ANIMAL NUTRITION. 
Effects on Total Metabolism. 
In the preceding paragraphs the effects of an exclusive proteid 
diet upon the proteid metabolism have been discussed. There 
remain to be considered its effects upon the metabolism of fat. 
Prorerps SUBSTITUTED FoR Bopy Fart.—When proteids are 
given to a fasting animal the proteid metabolism is increased, as we 
have seen, but at the same time the loss of body fat is diminished. 
Pettenkofer & Voit * fed a dog with varying amounts of lean 
meat, which may be regarded as consisting chiefly of proteids 
together with small amounts of fat, with the following average 
results in terms of nitrogen: 
Nitrogen Nitrogen ain or Loss Gain or Loss 
spree of Food, Metabolized, a Nitrogen, of Fat, 
. Grms. Grms. Grms. Grms, 
Ot 0 5.6 —5.6 —95 
500 17.0 20.4 —3.4 —47 
1000 34.0 36.7 —2.7 —19 
1500 + 51.0 ° 51.0 0 +4 
Rubner § has obtained a similar result by the use of the proteid 
mixture resulting from the extraction of lean meat with water, and 
which still contained some fat. As compared with the fasting state, 
the consumption of 740 grams of the moist material (containing 
72.2 per cent. of water) produced the following effect: 
; Nit 
Aoroecwer Food,| Metabolized, Metatrlized, 
; Grms. Grms, 
Fasting, si.oecci8-e0s oa eee 0 5.25 84.39 
POO e556 0d ei ehe sede eane o0,22 26.37 28.37 
Difference...... AE: 421.12 — 56.02 
The increased nitrogen cleavage resulting from an increase in 
the proteid supply liberates a certain amount of energy for the vital 
activities of the body, while the non-nitrogenous residue of the cleav- 
* Zeit f. Biol., 7, 489. 
+ Average of first two experiments, p. 84, Chapter IV. 
{ SeriesI only. The others showed a greater gain of fat and of nitrogen. 
§ Zeit. f. Biol., 22, 51. 
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