CHAPTER IV
Milk as a Food
Milk is first of all the food for the young,—until a
certain age the only food, and a perfect food. It contains
but little refuse or waste and is under favorable
conditions almost wholly digestible.
NUTRIENTS
All foods contain certain groups of nutrients which may be classified according to various functions in nutrition and their chemical composition.
Protein.—The protein group of nutrients contains
nitrogen and is necessary for building up the tissues
of the body, the muscles and the tendons which also
contain nitrogen. Only by this group can tissues
wasted by constant wear and tear be rebuilt. Proteins
are the flesh-forming group. To some degree the proteins
or albuminoids are also active in producing fat
in the body, but the other groups of nutrients, especially
the fats, also contribute.
Fats and Carbohydrates.—Another important function
of food is to produce and maintain the animal
heat. The main sources of this necessity are the fats
and the carbohydrates, so called because they consist
of the element carbon combined with oxygen and
hydrogen, the last two in the exact proportion in which
they are combined in water. All of these three groups
furnish the fuel, so to speak, for the body, but they
