THE SKIN 395 



between this point and the axis of the lever, 

 multiplied by one-tenth, will give the bending 

 pressure of the hair in the fraction of a gram. 

 Make ten observations on each hair and mark the 

 mean bending value on the wooden handle. 



Touch Discrimination. 1. Close the eyes and 

 let an assistant test the different parts of the 

 skin of the hand, arm, and face for discrimina- 

 ting power. For each test separate the points of 

 the sesthesiometer until they can be felt as two 

 (ordinary drawing dividers or compasses can be 

 used for an sesthesiometer). 



Eecord your results in millimetres for finger- 

 tips, palm of hand, back of fingers, back of hand, 

 back of wrist, flexor and extensor surfaces of fore- 

 arm, forehead, cheeks, lips, and tongue. 



2. Separate the points of the sesthesiometer 

 about 20 mm., and draw them gently side by 

 side along the extensor surface of the forearm 

 from the elbow to the wrist. Kepeat the experi- 

 ment on the flexor surface. Try the same for 

 the cheek and lips, beginning near the ear and 

 drawing the points so that one shall go above 

 and the other below the mouth. 



Describe the sensation in each case, and sug- 

 gest an explanation. 



"Weber's Law. Place the hand palm upward 

 in a comfortable position on the table. Close 



