
AVAILABILITY AND FUEL VALUE OF FOOD MATERIAIS. 85 
usual way as components of an ordinary mixed diet. Fortu- 
nately we have a means for obtaining a reasonably definite 
idea as to their accuracy under the latter conditions. There 
are now on record the results of about roo American digestion 
experiments with men on mixed diet. Most of these were 
conducted by Prof. C. EK. Wait at the University of Tennessee, 
Knoxville, and by the writers and associates. In these ex- 
periments 13 persons have served as subjects. The diet in 
each case was simple and made up of common food materials, 
and was entirely normal in amount, proportions of ingredients 
and method of cooking. In each experiment the ingredients 
of the feces were compared with the total amounts of nutrients 
in the food. The coefficients of availability thus obtained 
apply therefore to the total food eaten and not to the individ- 
ual food materials. Now if the coefficients of availability 
which were assumed for the different kinds of food materials 
as above described represent the actual availability of the same 
materials when they are eaten in mixed diet, then by applying 
them to the materials consumed in these experiments we 
should get estimated results which would agree with those 
found by experiment. We may therefore use the agreement 
or disagreement of the estimated availability of the total nu- 
trients of the diet used in these experiments with the results 
actually found as a measure of the correctness of the assumed 
coefficients of availability. This has actually been done. 
Using the coefficients as first assumed there was some discrep- 
ancy between the computed and experimental results. The 
coefficients were slightly altered, the change being such as 
seemed to us most probably correct and the computations were 
repeated. In this way coefficients were found which brought 
results agreeing very closely with those of actual experiments. 
In selecting coefficients for availability, food materials were 
divided into the following groups: (1) Animal food materials, 
as meats, fish, milk, etc. (2) Cereals such as wheat flour, 
corn (maize) meal, etc. (3) Sugars and starches. (4) Veg- 
etables, as potatoes, cabbage, turnips, etc. (5) Fruits. 
The coefficients of availability assumed are shown in the 
following table.* 

* The details of the calculations of which this and the following tables summarize 
the results will probably appear in a Bulletin of the Office of Experiment Stations. 
iP 
