CHAPTER IX
THE SENSES
Experiment 1. Where are the Nerves of Touch most Abundant?—Open a pair of scissors so that the points are one eighth of an inch apart, and touch both points to the tip of the finger. Are they felt as one or as two points? Find how far they must be separated to be felt as two points when applied to the back of the neck. Record results. Caution: The person should be blindfolded, or should look away while the tests are being made. Two pins stuck in a cork will be more convenient to use than scissors.
Experiment 2. Nerves of Temperature, or Thermic Nerves.—Draw the end of a cold wire along the skin. Does the wire feel cold all the time? Repeat with a hot wire. Do you conclude that temperature is felt only in spots?
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Fig. 119.—"Cold" Spots (light shading). "Hot" Spots (dark), skin of thigh.
Muscular Sense.—Experiment 3.
Make tests of the ability to distinguish
the weight of objects weighing
nearly the same, when laid by another
in outstretched hand; also by laying
them in the hand while it rests upon
a table. Which test showed more
delicate distinctions? In which were
muscles brought into use? Experiment 4. Close the eyes and let some
one move your left arm to a new position; then see if you can with the
forefinger of the right hand touch the forefinger of the left hand in its
new position at the first attempt.
Experiment 5. Functions of the Several Parts of the Tongue.—Test the tip, edges, and back of the tongue with sugar, vinegar, quinine, and salt. Where is the taste of each most acute? Record results.
Flavors.—Experiment 6. Blindfold a member of the class, and while he holds his nostrils firmly closed by pinching them, have him place successively upon his tongue a bit of potato and of onion. Can he distinguish them? Experiment 7. Mark F after each of the following
