e found in the tissues?

PRACTICAL WORK

Illustrate the ordinary meaning of the term "absorption" by bringing the
end of a piece of crayon in contact with water, or a piece of blotting
paper in contact with ink, noting the passage of the liquid into the
crayon or the paper. Show how absorption from the food canal differs from
this kind of absorption.

Show by a diagram similar to Fig. 77 the two routes by which the foods
pass from the alimentary canal into the blood stream.

CHAPTER XII - ENERGY SUPPLY OF THE BODY

If one stops taking food, it becomes difficult after a time for him to
move about and to keep warm. These results show that food has some
relation to the energy of the body, for motion and heat are forms of
energy. The relation of oxygen to the supply of energy has already been
discussed (Chapter VIII). We are now to inquire more fully into the energy
supply of the body, and to consider those conditions which make necessary
the introduction of both food and oxygen for this purpose.

*Kinds of Bodily Energy.*--The healthy body has at any time a considerable
amount of _potential_, or reserve, energy,--energy which it is not using at
the time, but which it is able to use as its needs require. When put to
use, this energy is converted into such forms of _kinetic_ energy(69) as
are indicated by the different kinds of bodily power. These are as
follows:

1. _Power of Motion._--The body can move itself from place to place and it
can give motion to things about it.

2. _Heat Power._--The body keeps itself warm and is able to communicate
warmth to its surroundings.

3. _Nervous Power._--Through the nervous system the body exercises the
power of control over its different parts.

As motion, heat, and nervous power the body uses most of its energy.

*The Source of Bodily Energy.*--As already indicated, the energy of the
body is supplied through the food and the oxygen. These contain energy in
the potential form, which becomes kinetic (active) through their uniting
with each other in the body. Somewhat as the power of the steam engine is
derived from the combustion of fuel in the furnaces, the energy of the
body is supplied through the oxidations at the cells. How the food and
oxygen come to possess energy is seen by a study of the general methods by
which energy is stored up and used.

[Fig. 81]

Fig. 81--*Simple device* for storing energy through gra