306 PRINCIPLES OF ANIMAL NUTRITION. 
N.-fr. Extract N -fr. Extract Digested N -fr. 
of Hay, of Feces, Extract. 
Cals. per Gram. Cals. per Gram. Cals. per Gram. 
Nh ceahen AeA tes settee aera acted 4.5713 5.2834 4,203 
Db sb dk or had eines een d 4.6547 5.4212 4.146 
LE a8 2 cena eaten oer eee ae 4.5029 5.1058 4.246 
TEV sea a Siz uh e meer tae ema eos wes 4.6081 5.2484 4.335 
AVETAROs. ii dale dace $s 4.584 5.265 4.232 
In view of the indirect nature of the computation the results 
agree as well as could be expected and show that, as might be 
anticipated from its chemical composition, the heat of combustion 
of the digested portion of the nitrogen-free extract did not vary 
widely from that of starch. 
Dicestep Matter or Mixep Rations.—The Méckern experi- 
ments afford accurate data as to the energy of the total digested 
matter of a large number of mixed rations. Kellner * has com- 
pared this with the computed energy of the same material. For 
this computation the factors used were: for fat, 8.322 Cals. per gram; 
for crude fiber and nitrogen-free extract, the average of Stohmann’s 
figures for starch and cellulose, 4.184 Cals. per gram; for protein 
provisionally, 5.711 Cals. per gram. Of the fifty-nine experiments, 
twelve, in which large amounts of wheat gluten or oil were fed, 
showed sufficient differences to indicate that the figures assumed 
for protein and fat were too low as applied to these two materials. 
In the other forty-seven cases the differences were nearly all less 
than 2 per cent. of the total amount and were in both directions. 
The special interest of these results lies in the fact that they 
show that we may safely use the above figures as indicated on p- 
302 to correct the results reached from a comparison of two rations. 
NITROGEN-FREE Extract or Starcu.—As an example of Kell- 
ner’s method of computation we may compare the results for Ox H 
in Period 3, with starch, and in Period 4, on the basal ration. The 
total energy of the apparently digested matter (compare Table 
IV of the Appendix) was— 
Period 3, with starch.............. 28,718 Cals. 
Period 4, without starch.............. 21,763 
Difference...... Rea siee arrest 6055 © 
* Loc, cit., 58, 407. 
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