THE FOOD AS A SOURCE OF ENERGY. 321 
Difference in wrap; 
Protein eee i a ome ence 
(N X6.25) per Grm. 
Digested, Per Grm. of | Digestible 
Grms. Total, Protein Protein, 
Cals. Digested, Cals. 
Cals. 
Meadow Hay: 
Nos: lj) Ox Avis acuwiexeas 440 1991.3 4.526 1.185 
HoT Tt) Wie Vacs dye dak 342 1686.9 4.933 0.778 
SE No OV WS asa lea mutsae ara 137 583.2 4.257 1.454 
Sm Aree Creer e ara nearer 146 556.5 3.812 1.899 
“ VI, “ HH, Period 1... 193 781.4 4.049 1.662 
fe ONT Og 8 yee 220 798 .0 3.632 2.079 
EO ML OO Jah oe ge. ese 213 930.5 4.368 1.343 
AB OE Muon antse a cer sea ace 413 1925.7 4.662 1.049 
BE Ba Se Via csi Gunton 451 1559.3 3.456 2.255 
BE SB SO VT ioc Abra ds 458 1737.9 3.794 1.917 
BE MG I oie Sh ictieae oa as 540 3224.6 5.973 —0.262 
Average ..........0005 323 1434.1 4.439 1,272 
Oat Straw : 
No, I, Ox Fisinssse yess 35 354.2 10.120 —4.409 
OO TD A Gas Sasbatieds ox 48 274.0 5.710 —0.001 
AVEPABE: ti Sidon eats es 42 314.1 7.478 —1.767 
Wheat Straw : 
Nowy Ox Hie cgecaeesndk —-11 289.7 (2?) (?) 
Bg SP ad, cals aces Gran. hae 14 413.2 29.520 —23 .809 
Average ...........0.. 2 351.5 (2?) (2) 
* Corrected to nitrogen equilibrium. 
animals and consequently that the metabolizable energy of the 
proteids cannot be widely different. In these results upon coarse 
fodders we meet an apparent contradiction of this conclusion, the 
metabolizable energy of the digestible protein as above computed 
being quite variable and much lower than the values found for pure 
proteids, while in the straw we get large negative values. 
These latter results, however, while appearing at first sight para- 
doxical, furnish the clue to the apparent contradiction. In the 
ease of the straws it is evident that a very considerable part of the 
potential energy of the urine must have been contained in non- 
nitrogenous substances, and that the latter must have been derived 
largely from the non-nitrogenous matter of the food. We have 
already seen, however, that these non-nitrogenous excretory prod- 
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