200 STORRS AGRICULTURAL EXPERIMENT STATION. 
digestible nutrients in a considerable number of dietaries. Sim- 
ilar attempts have been made by the writer from time to time.* 
It has been the custom of both American and European 
chemists and physiologists, for a number of years, to make use 
of the figures for digestible nutrients in estimating the nutri- 
tive values of feeding stuffs and in calculating the rations for 
domestic animals. ‘This has seemed to be warranted by the 
number of experiments in which the digestibility of feeding 
stuffs has been determined by actual tests. 
The tests of the digestibility of food by man reported up to 
the present time are much less numerous than those of feeding 
stuffs by domestic animals, at the same time the variety of 
materials in common use, as food of man, is much larger than 
that of feeding stuffs for animals. It would thus seem, at first 
thought, that while the data may be sufficient for the setting 
up of coefhicients of digestibility of feeding stuffs and basing 
calculations upon them, the information thus far accumulated 
is still too small to warrant us in applying the same principle 
to food materials. 
There are, however, some considerations in favor of the use 
of the coefficients of digestibility for the food of man. In the 
first place our ordinary food materials are so much more easily 
and completely digestible than feeding stuffs that the undi- 
gested residue of food as used in ordinary diet under normal 
conditions by men, women, and children make a much smaller 
proportion of the whole than is the case with feeding stuffs as 
eaten by domestic animals. ‘The variations in digestibility are 
likewise much less with the food of man. Indeed, this is 
specially the case with animal foods and with the carbohydrates 
which are the principal constituents in most vegetable foods. 
The variations in the digestibility of protein in the vegetable 
foods are somewhat wider. ‘The determinations of the digesti- 
bility of fats of most vegetable foods, by the methods commonly 
followed, bring very uncertain coefficients of digestibility, 
because of the very small quantities of fats. ‘Ihe errors here, 
however, are of less practical consequence, because the fats of 
the vegetable foods make so small a proportion of the total diet. 
One great difficulty with the larger number of digestion 
experiments hitherto made with man is found in the fact 

* Bulletin 21, Office of Experiment Stations, p. 71.. See also, Century Magazine, 
September, 1887. . 
