THE FOOD AS A SOURCE OF ENERGY. 321 
S Dern in Metaboli 
7" mergy of Urine.* etaboliz- 
Prot 
(NX6-25), pre 
Digested, Per Grm. of igestible 
Grms. Total, Protein Protein, 
Cals. Digested, Cals. 
als. 
Meadow Hay: 
No. I, Ox A............ 440 1991.3 4.526 1.185 
PN aU eee Lllven cise ans neo 342 1686.9 4.933 0.778 
OE Vg BO TS out einai a 137 583 .2 4,257 1.454 
et Vag i AGE tes Ce 146 556.5 3.812 1.899 
“ VI, “ 4H, Period 1... 193 781.4 4.049 1.662 
NI, He Cee 220 798 .0 3.632 2.079 
Oe Le — dren et ooh 213 930.5 4.368 1.343 
ofa: aa. Satan) 8 ne ee 413 1925.7 4.662 1.049 
AB SMEs cape evs’ Ws 451 1559.3 3.456 2.255 
OS VB er 88 MT ve acne tee God 458 1737.9 3.794 1.917 
LS) Doaiaat g), G, Goren i demir es 540 3224.6 5.973 —0.262 
Average ..........00005 323 | 1434.1 4.439 1,272 
Oat Straw : 
No. TI, Ox Fue... cece es 35 354.2 10.120 —4.409 
Oe ET 8 A coun Stace aerate 48 274.0 5.710 —0.001 
Average ..........0055 42 314.1 7.478 —1.767 
Wheat Straw : 
No. I, Ox H............. Sai 289.7 (?) (2) 
STG Mh asin cs wiataenvotene S 14 413.2 29.520 —23.809 
Average ............0. 2 851.5 (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 
case 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- 
