THE FOOD AS A SOURCE OF ENERGY. 275 
metabolized had substantially the same composition and heat-value 
as the lean meat of the first experiment, and the feces are also 
assumed to be similar. 
Nitrogen of | Nitrogen of | Nitrogen of 
Food. Tood, Feces, Urine, 
Grms. Grms. Grms. 
Lean meat ............... 0.1540 0.0024 0.1516 
Extracted lean meat ....... 0.1659 0.0023 0.1636 
Nothing (body tissue)...... 0.1659 0.0023 0.1636 
The energy of the excretory products, calculated per gram of 
nitrogen, was as follows: 
Food. Urine, Feces, 
Cals. Cals. 
Lean meat ..............05 7.450 70.290 
Extracted lean meat ....... 6.695 81.515 
Nothing seccac tid nt ate ne ont 8.495 
A comparison of the above results for the urine with the energy 
of urea (5.41 Cals. per gram of nitrogen) fully confirms the conclu- 
sions already drawn from its chemical composition. 
From the figures of the last two tables, together with the heats 
of combustion found for the food consumed, viz., 
Lean meat, fat removed................ 5.345 Gals. per gram 
« «extractives and fat removed...5.754 “ “ « 
we can readily compute the energy of the excreta and by difference 
the metabolizable energy of the food per gram, as follows: 
Extracted Nitrogenous 
Lean Meat. Lean Meat. Body Tissue. 
Energy of food .............+.[.....-|5-3450)..... .|5.7540]......|5.3450 
aii g (Meee knee ete 0.1683]...... 0.1854]...... 0.1683 
oe _ AP Ie alee ci ak eeu 1.1204)... ... 1.0945}... ... 1.2878 
Metabolizable energy .......... 4.0473)...... 4 4741 Senate 3.8889 
5.3450 
5. 3450/5 7540)5.7540 5 3450)5.3450 
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