CHAPTER IX 



THE SENSES 



Experiment i . 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 con- 

 venient 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 ? 



Muscular Sense. Experiment 3. 

 Make tests of the ability to distin- 

 guish 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 ? Experi- 

 ment 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, qui- 

 nine, 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 Rafter each of the following 



142 



FIG. 119. " COLD" SPOTS (light 

 shading). " HOT" SPOTS (dark), 

 skin of thigh. 



