in, and in the fatter meats it is larger. Cheese is rich in both
protein and fat. Among the vegetable foods, dried beans and peas are
especially rich in protein. The proportion in oatmeal is also fairly
large, in wheat it is moderate, and in maize meal and rice it is rather
small. Oats contain more oil than any of the common cereals, but in none
of them is the proportion especially large. The most abundant nutrient
in all the cereals is starch, which comprises from two-thirds to
three-fourths or more of their total nutritive substance. Cotton-seed is
rich in edible oil, and so are olives. Some of the nuts contain fairly
large proportions of both protein and fat. The nutrient of potatoes is
starch, present in fair proportion. Fruits contain considerable
carbohydrates, chiefly sugar. Green vegetables are not of much account
as sources of any of the nutrients or energy.

Similar food materials from different sources may also differ
considerably in composition. This is especially true of meats. Thus, the
leaner portions from a fat animal may contain nearly as much fat as the
fatter portions from a lean animal. The data here presented are largely
those for American food products, but the available analyses of English
food materials indicate that the latter differ but little from the
former in composition. The analyses of meats produced in Europe imply
that they commonly contain somewhat less fat and more water, and often
more protein, than American meats. The meats of English production
compare with the American more than with the European meats. Similar
vegetable foods from the different countries do not differ so much in
composition.

4. _Digestibility or Availability of Food Materials._--The value of any
food material for nutriment depends not merely upon the kinds and
amounts of nutrients it contains, but also upon the ease and convenience
with which the nutrients may be digested, and especially upon the
proportion of the nutrients that will be actually digested and
absorbed. Thus, two foods may contain equal amounts of the same
nutrient, but the one most easily digested will really be of most value
to the body, because less effort is necessary to utilize it.
Considerable study of this factor is being made, and much valuable
information is accumulating, but it is of more especial importance in
cases of disordered digestion.

TABLE II.--_Coefficients of Digestibility (or Availability) of
Nutrients in Different