the experience. So also can
the efficiency of an individual or a nation, as compared with other
individuals or nations, be determined. The inefficient are those who
repeat the same error or useless act over and over, or else fail to
repeat a chance useful act whose repetition might lead to success. They
are unable to learn their lesson and be guided by experience. Their past
does not sufficiently minister to their present, and through it direct
their future.

2. HOW PAST EXPERIENCE IS CONSERVED

PAST EXPERIENCE CONSERVED IN BOTH MENTAL AND PHYSICAL TERMS.--If past
experience plays so important a part in our welfare, how, then, is it to
be conserved so that we may secure its benefits? Here, as elsewhere, we
find the mind and body working in perfect unison and harmony, each doing
its part to further the interests of both. The results of our past
experience may be read in both our mental and our physical nature.

On the physical side past experience is recorded in modified structure
through the law of habit working on the tissues of the body, and
particularly on the delicate tissues of the brain and nervous system.
This is easily seen in its outward aspects. The stooped shoulders and
bent form of the workman tell a tale of physical toil and exposure; the
bloodless lips and pale face of the victim of the city sweat shop tell
of foul air, long hours, and insufficient food; the rosy cheek and
bounding step of childhood speak of fresh air, good food and happy play.

On the mental side past experience is conserved chiefly by means of
_images_, _ideas_, and _concepts_. The nature and function of concepts
will be discussed in a later chapter. It will now be our purpose to
examine the nature of images and ideas, and to note the part they play
in the mind's activities.

THE IMAGE AND THE IDEA.--To understand the nature of the image, and then
of the idea, we may best go back to the percept. You look at a watch
which I hold before your eyes and secure a percept of it. Briefly, this
is what happens: The light reflected from the yellow object, on striking
the retina, results in a nerve current which sets up a certain form of
activity in the cells of the visual brain area, and lo! a _percept_ of
the watch flashes in your mind.

Now I put the watch in my pocket, so that the stimulus is no longer
present to your eye. Then I ask you to think of my watch just as it
appeared as you were looking at it; or you may yourself choose to th