THE FOOD AS A SOURCE OF ENERGY. 3°97 
A slightly less amount of the basal ration was eaten in Period 3 
than in Period 4. The difference in crude nutrients and in esti- 
mated digestible nutrients was as follows: 
Estimated Digestible. 
Total, 
Grms. : 
Equi t 
crm, | awit 
Fee. agen 4 2 11.4 
rude fiber............. 13 
Nitrogen-free extract.... 23 2s LOOu 
111.8 
This amount of 112 Cals. should be added to the energy of 
the digested matter of Period 3 or subtracted from that of Period 4 
in order to render them comparable, thus making the real difference 
due to the starch 7067 Cals. Still further, the starch diminished 
the digestibility of the other nutrients of the ration by the following 
amounts: 
Equivalent 
Gras: Buerey Cale; 
Protein...........- 118 673.8 
Crude fiber........ 17 71.1 
Ether extract...... 9 74.9 
819.8 
Had these amounts been digested in Period 3 as in Period 4, the 
energy of the digested matter of the ration would have been 820 
Cals. greater, and the difference between the two periods would 
have been 7887 Cals. The digestible nitrogen-free extract was 
1876 grams more in Period 3 than in Period 4. Assuming all of 
this to be derived from the starch, we have for the energy of each 
gram of digested nitrogen-free extract 7887-- 1876= 4.204 Cals. 
The following table* contains the results of all the starch 
experiments computed in the manner just outlined: 
* Loc. cit., 58, 412. 
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