Without going into detail of the investigations carried out on absorption in
these countries we may say with Hutchison that, "taking the general results of
all experiments, it is calculated that the following proportions of the nutritive
constituents will be absorbed from a mixed diet "*:—

  Protein. Carbohydrate. Fat.
Animal foods . 98% 100% 97%
Cereals and Sugars . 85% 98% 90%
Vegetables and Fruit . 80% 95% 90%

    Later experiments, particularly in America, appear to give lower figures
specially for the cereals and legumes; however, we may accept it that the co-efficient
of absorption is very high.

    These results were obtained from experiments on batches of one, two, three or
four men observed for one, two or more days. The batch was put on a "basal"
diet—a known diet from which a known amount of protein, carbohydrate and fat
would be absorbed; then to the basal diet the food material to be examined was
added. By calculation from the result of chemical analysis of the excreta before
and after the new food material was added the co-efficient of absorption of the
proximate principles is obtained in the usual way. This is the method—intro-
duced by Bryant and Milner—that we made use of in our investigations. It
was modified to suit the special conditions of our work.

    By this method or others on the same lines, the co-efficient of absorption of
the alimentary principles of the separate food-stuffs composing a diet in Europe
and America have been worked out, and fixed figures are published representing
the percentage of protein, carbohydrate or fat that is absorbed from any of the food
materials in use in those countries. Thus for protein according to Atwater we find
the co-efficient of digestibility given for the several classes of food was follows:—

Soups     co-efficient of digestibility 97%
Crackers (biscuits) " " 83—85%
Legumes (average) " " (about) 76%

   The results of our investigations would appear to show that no fixed figures
for the co-efficient of absorption—at least for protein—of the different food

*Hutchison, page 14.

Atwater: Storrs Agricultural Experiment Station, 9th Annual Report 1896.