VEGETABLE FOODS.
The large and varied class of food-stuffs derived from plants
have a strikingly common feature as far as their chemical
composition goes. They are all very rich in carbohydrates,
and as a rule are poor in fats. They contain vegetable
proteins in different proportions, and also an abundant pro-
portion of water.
Vegetable proteins exist as vegetable albumin and vegetable
casein. They are not so easily digested and assimilated as
animal proteins. The proteins in peas and beans are rich in
sulphur, and are therefore prone to induce flatulence.
Though there is no true gelatine substance in carbo-
hydrates, there is a peculiar group of bodies known as
" peotoses.'' These substances give to fruits their power of
forming jellies when boiled.
On the whole, plant life is not rich in fats. The fat
resembles in chemical composition the animal fats, but con-
tains, as a rule, more of the oily constituent (olein) and less
of the solid components. The solid vegetable fats are cocoa-
nut oil and cocoa butter, none of which are in great use as
foods.
Vegetable butters are now made from mixtures of these
fats, and closely resemble cooking and table butter. In

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74 THE BOOK OF DIET.
addition to the oils obtained by pressure, most plants contain
volatile or essential oils, to which they owe their fragrance.
These are mainly used in perfumery, but they enter also
largely into flavouring agents, and act as condiments to
excite the appetite and stimulate the digestive juices.
The salts of plants exist largely as salts of potash and
phosphorus ; in many of the cereals — for example, wheat —
iron is also present in combination with phosphoric acid.
