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 think of it without my suggesting it
to you. In either case the cellular activity in the visual area of the cortex is
reproduced approximately as it occurred in connection with the percept, and lo!
an image of the watch flashes in your mind. An image is thus an approximate
copy of a former percept (or several percepts). It is aroused indirectly by means
of a nerve current coming by way of some other brain center, instead of directly
by the stimulation of a sense organ, as in the case of a percept.
If, instead of seeking a more or less exact mental picture of my watch, you only