e, are we able to enter
fully into the wonderful world about us and receive the stimuli
necessary to our thought and action.

4. PROBLEMS IN OBSERVATION AND INTROSPECTION

1. Observe a schoolroom of children at work with the aim of discovering
any that show defects of vision or hearing. What are the symptoms? What
is the effect of inability to hear or see well upon interest and
attention?

2. Talk with your teacher about testing the eyes and ears of the
children of some school. The simpler tests for vision and hearing are
easily applied, and the expense for material almost nothing. What tests
should be used? Does your school have the test card for vision?

3. Use a rotator or color tops for mixing discs of white and black to
produce different shades of gray. Fix in mind the gray made of half
white and half black; three-fourths white and one-fourth black;
one-fourth-white and three-fourths black.

4. In the same way mix the two complementaries yellow and blue to
produce a gray; mix red and green in the same way. Try various
combinations of the four fundamental colors, and discover how different
colors are produced. Seek for these same colors in nature--sky, leaves,
flowers, etc.

5. Take a large wire nail and push it through a cork so that it can be
handled without touching the metal with the fingers. Now cool it in ice
or very cold water, then dry it and move the point slowly across the
back of the hand. Do you feel occasional thrills of cold as the point
passes over a bulb of Krause? Heat the nail with a match flame or over a
lamp, and perform the same experiment. Do you feel the thrills of heat
from the corpuscles of Ruffini?

6. Try stopping the nostrils with cotton and having someone give you
scraped apple, potato, onion, etc., and see whether, by taste alone, you
can distinguish the difference. Why cannot sulphur be tasted?

CHAPTER VII

PERCEPTION

No young child at first sees objects as we see them, or hears sounds as
we hear them. This power, the power of perception, is a gradual
development. It grows day by day out of the learner's experience in his
world of sights and sounds, and whatever other fields his senses respond
to.

1. THE FUNCTION OF PERCEPTION

NEED OF KNOWING THE MATERIAL WORLD.--It is the business of perception to
give us knowledge of our world of material _objects_ and their relations
in _space_ and _time_. The material world which we enter through the
gateways of the