436 MAN BECOMES THE CONQUEROR OF THE WORLD 



Experiment further on various parts of the body, and record the re- 

 sults in the form of a table. 





Place Touched 



Distance between Points 



Back of Hand . . 







Palm of Hand . . 







Finger Tips . . . 







Wrist . ' . . . . 







Upper Arm . . . 







Back of Neck . . 







Back 







Which part of the body seemed most sensitive to touch ? 



Laboratory Exercise. With a ruler and a pen, draw a square inch 

 on the underside of your wrist. Heat a wire nail until it feels 

 very hot. Now lightly touch all parts of the skin within the square 

 area. Do all parts feel the heat, or only the sense of slight pressure 

 of the nail? Mark with a little cross all spots that are sensitive to 

 heat. 



Xow cool off the nail by placing it on ice. Wipe it dry and apply 

 while still cold in the same way to the area marked off on the wrist. 

 Do you feel the sensation of cold in all spots? Mark as before, this 

 time using a dot. 



Do all parts of the skin feel heat and cold? What does this mean? 



Laboratory Exercise. What is the relation between taste and smell ? 



Cover your eyes and hold your nose tightly with the fingers. 

 Have another pupil place on your tongue very small pieces of peeled 

 apple, peeled raw potato, peeled raw turnip, and onion. Have the 

 pieces exactly the same taste? Have some one record the results. 

 Are you aware of the different flavors ? Are you aware of them with 

 the nostrils open? Try the experiment with a number of other sub- 

 stances, as sugar, vinegar, vanilla, mustard, salt, and spices. 



Rub the tongue dry. Place a little sugar on it. In what condition 

 must materials be in order to be tasted ? 



In tabular form note those substances which are recognized by 

 taste only and those which are recognized by taste and smell. 



