EXPERIMENTS ON DIGESTION OF FOOD BY MEN. 165 
Digestion experiments with men living on an ordinary mixed 
diet present no serious difficulty and it is fair to assume that 
the results may often be nearer approximations to the normal 
digestion than those of experiments with single food materials. 
The experiments here reported have been with single food 
materials and with mixed diet. ‘Those with mixed diet are of 
the most consequence for the present report, not only because 
they apparently represent more nearly the digestibility of foods 
as ordinarily eaten, but because of the use made of them in a 
discussion in the article which follows. 
In a compilation of the results of investigations of this sort . 
made previous to 1895,* accounts were given of all the experi- 
ments which the writer and his associates found in the litera- 
ture of the subject and which seemed accurate enough to be 
used for statistical inferences. Nearly all the experiments had 
been made in Europe; more had been made in Germany than 
in any other country. The total number of individual experi- 
ments included in the compilation was less than one hundred 
and fifty. Of this number 114 were with men, five with 
women, and 13 with children. It is evident, therefore, that 
the results thus far obtained are far from sufficient, and 
the desirability of further inquiry in this line is very 
clear. In connection with the investigations on the nutrition 
of man which are being carried out by the Department of 
Agriculture in Washington in cooperation with experiment 
stations and other institutions, quite a number of digestion 
experiments have already been made and others are in progress. 
There is reason to hope, therefore, that results of no little value. 
will gradually accumulate.. 
EXPERIMENTAL METHODS FOLLOWED. 
As the methods in common use for investigations of this 
sort have been described by the writer elsewhere,* a detailed 
description is hardly necessary here. It will suffice to say that 
in the experiments here reported the food and the feces were 
analyzed by the usual methods, and that the weights and com- 
position of the materials are taken as showing the total amounts 
of nutrients in the food and the amounts left undigested in the 
feces. Subtracting the undigested residue from the total 
amount shows the amount actually digested. 
* Bulletin 21 of the Office of Experiment Stations, pp 56-73. 
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