completely ripened. Green fruits contain less sugar than do ripe ones,
and so they are more sour to the taste. In some cases, the carbohydrate
found in green fruits is partly in the form of starch, which in the
process of development is changed to sugar. The cellulose of green
fruits, especially that distributed throughout the pulp of the fruit
itself, is usually tougher and harder than that which is found in the
same fruit after it has ripened.

22. DIGESTIBILITY OF FRUITS.--The ripeness and freshness of fruits
determine their digestibility to a great extent, but the peculiarities
of each person have much to do with this matter. Many times a particular
fruit will agree with almost every one but a few exceptional persons,
and, for no apparent reason except their own peculiarities of digestion,
it disagrees very badly with them. Abnormal conditions of the alimentary
tract, however, cannot be taken into consideration in a general
discussion on the digestibility of foods, for it is a subject that
cannot be treated except from a dietetic standpoint. A safe rule to
follow when a fruit is found to disagree with a person is to omit it
from that person's diet. This need not prove a hardship, for the wide
range, or variety, of fruits makes it possible to find one or more kinds
that will agree with each person.

23. As has been explained, sugar is the food material from which the
nutritive value of fruits is obtained. With the exception of a few
predigested foods, manufactured in such a way that they can be digested
easily, this sugar is probably the most easily digested form of food
that can be obtained. This substance, being held in solution in the
fruit juices, which are encased in a cellulose covering, depends to some
extent for its digestion on the hardness of the cellulose. When this
covering is old and hard or green and tough, as the case may be, it is