_Fats._--Butter belongs to the class of food-stuffs known as fats. It
increases the fuel value of those dishes to which it is added.
Fats supply heat and energy to the body in a concentrated form. For this
reason they should be used in a limited quantity. Fats undergo several
changes during the process of digestion, and the excessive use of them
interferes with the digestion of other foods and throws a large amount
of work upon the digestive organs. Cooked fats are more difficult of
digestion than uncooked fats, and other foods cooked with hot fat are
rendered more difficult to digest.
_Vegetables._--Vegetables should be used when in season, as they are
always best and cheapest then. They are better kept in a cold, dry, and
dark place.
If the vegetables contain starch or tough cellulose, they will require
cooking; as raw starch is indigestible, and the harsh cellulose may be
too irritating to the digestive tract.
In old or exceedingly large vegetables the cellulose may be very tough;
hence a long period of cooking is necessary. They should be cooked only
until they are tender. Longer cooking may destroy the flavour, render
the vegetables difficult of digestion, and cause the colour to change.
In very young vegetables the cellulose is delicate and, if young
vegetables do not contain much starch, they may be eaten raw.
When cooked vegetables are served, they are usually seasoned and dressed
with butter (for one cup of vegetables use 1/2 teaspoonful of salt, 1/8
teaspoonful of pepper, and 1/2 tablespoonful of fat), or a sauce is
prepared to serve with them.