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?
- 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? - 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. - 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. - 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? - 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?