414 PRINCIPLES OF ANIMAL NUTRITION. 
the study of replacement values by Rubner’s method the latter 
factor was not necessary, but for a determination of the percentage 
availability of the energy of the food it is indispensable. In the 
following paragraphs the necessary’ computations of energy have 
been made by the writer, using Rubner’s factors so far as possible.* 
In the case of Pettenkofer & Voit’s experiments the average 
results given in Chapter V have been made the basis of the compu- 
tation. 
Prorerps.—From the average results obtained by Pettenkofer 
& Voit + with different amounts of lean meat (see p. 104), the met- 
abolizable energy of the food and of the resulting gain (or loss) by 
the body may be computed as follows: 
ee Computed Heat Production. 
+: . 
sais eee see 
Grms, Cals. ee. From Fat, Total, Cals. 
Gale.” Cals. Cals. 
0 0 146 895 1041 —1041 
500 442 530 443 973 —531 
1000 883 954 179 1133 —250 
1500 1325 1325 —38 1287 +38 
* The following factors were used in computing these experiments: 
Metabolizable Energy of Food : 
Bacon (Speck), 92.2 per cent. fat (Zeit. f. Biol., 30, 138). 
1 grm. pork fat, 9.423 Cals. (7bid., 21, 333). 
1 grm. butter fat, 9.216 Cals. (U.S. Dept. Agr., Office of Expt. Stations, 
Bull. 21, p. 127). 
1 grm. cane-sugar, 4.001 Cals. (Zeit. f. Biol., 21, 266). 
1 grm. grape-sugar, 3.692 Cals. (Stohmann, Zeit. f. Biol., 22, 40). 
1 grm. starch, 4.123 Cals. (Stohmann, zbid., 19, 376). 
Fresh lean meat, 3.4 per cent. nitrogen. 
1 grm. nitrogen in meat, 25.98 Cals. (Zeit. f. Biol., 21, 321). 
1 grm. nitrogen in syntonin, 26.66 Cals. (ibid., 21, 309). 
Energy of Metabolism : 
1 grm. excretory nitrogen (urine and feces). 
(a) No proteids fed : 
Birds, 24.35 Cals. (Zeit. f. Biol., 19, 367). 
Mammals, 24.94 Cals. (ibid., 22, 48). 
(b) Meat fed, 25.98 Cals. (Ibid.). 
(c) Syntonin fed, 26.66 Cals. (ibid.). 
1 grm. carbon in fat, 12.31 Cals. (ibid.). 
ft Zeit. f. Biol., 7, 489. 
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