chiefly concerned in getting rid of the waste products of protein.

_Carbohydrate_ is the name given the group of foodstuffs to
which the sugars belong. The food value of cane sugar, the most
familiar member of the group, was recognized even in prehistoric days
by the natives of India. By boiling the plant we call sugar-cane they
obtained a substance to which they gave the name Sakkara, and from
this our word sugar evidently originated. The roots of this plant
were carried into Europe and cultivated during the Middle Ages.
Obviously, its value was and is appreciated, since the cultivation of
the sugar-cane and the sugar-beet has become the foundation of a
great modern industry.

There are some persons, perhaps, who do not realize that beside cane
sugar many kinds of carbohydrate occur in our food. Glucose or grape
sugar, for example, occurs not only in the fruit indicated by its
name, but also in other fruits, in corn, in onions, and in the common
vegetables. Glucose is especially suited to act as nourishing food.
In keeping with that fact our digestive juices convert most of the
sugars we eat, if not all of them, into glucose, which is regularly
present in our blood. It is unnecessary to enumerate all or even the
more important compounds included in the carbohydrate group; but
everyone should know that starch is its chief member, and that after
being thoroughly digested starch enters the body as glucose and
therefore serves the same purpose as sugar.

The value of carbohydrates as a source of heat and energy may be
accurately measured, and is technically expressed in terms of a unit,
called the calorie. As the energy which our bodies require may be
estimated in the same terms, it is possible to determine whether or