
AVAILABILITY AND FUEL VALUE OF FOOD MATERIALS. 105 

The factors for fuel value in Table ro represent the available 
energy per gram. Corresponding values per pound can be 
readily computed by multiplying the values per gram by 
453.6, the number of grams in a pound. In the ordinary 
mixed diet the fuel value of one pound of protein as thus 
computed from the figures of Table ro is 1,820, of fat 4,040, 
and of carbohydrates 1,820 calories. The corresponding values 
per pound of available nutrients are 2,000, 4,260, and 1,860 
calories respectively. 
APPLICATION OF PROPOSED FACTORS FOR FUEL VALUE TO 
ACTUAL DIGESTION EXPERIMENTS. 
In the preceding pages the factors for availability and for 
heats of combustion have been applied to experimental data in 
such a way as to test their accuracy. Ina similar manner the 
reliability of the proposed factors for fuel value may be tested 
by applying them to the quantities of nutrients consumed in 
digestion experiments with mixed diet of more or less simple 
character, and comparing the computed fuel value of the diet 
with that actually found by experiment, z. ¢., the difference 
between the total energy of the food and that of the feces and 
urine. 
The results of a considerable number of digestion experi- 
ments are available for the purpose of such comparison. Thus 
far we have made the necessary calculations from the data of 
twenty-seven experiments carried on in this laboratory in con- 
nection with investigations with the respiration calorimeter.* 
In some of these the subject was outside the respiration appa- 
ratus, the study being preliminary to the more detailed expe- 
riments within the respiration chamber. ‘These are indicated 
in Table 11 beyond as “‘ordinary’’ experiments. In other 
experiments the subject was in the apparatus. These are 
indicated as ‘‘respiration’’ experiments. Hach ‘‘ordinary”’ 
experiment was immediately followed by one or more “ respi- 
ration’’ experiments with the same man. The kinds and 
amounts of food in the ‘‘ordinary’’ or preliminary experi- 
ments were very nearly the same as in the subsequent ‘‘ res- 
piration’’ experiments. 

* The details of the digestion experiments are to be published in a Bulletin of the 
Office of Experiment Stations of the U. S. Department of Agriculture, 
