PEESStJEE 



441 



The delicacy of pressure sense can be measured in two 

 ways, by determining the least amount of pressure necessary 

 to arouse a sensation, and by locating the least distance 

 apart at which two points can be felt as two. The method 

 of determining the first consists in varying the pressure 

 upon various portions of the body until the least amount 

 necessary to produce a sensation in any given part is de- 

 termined. The results of such tests show that the skin of 

 the face, forehead, and temples is most sensitive of all the 

 skin areas to the feeling of pressure. The back of the hand 

 is more sensitive in this respect than the tips of the fingers. 

 Two milligrams of pressure is necessary to arouse sensation 

 on the forehead, while from five to fifteen milligrams is 

 necessary when applied to the finger tips. Such tests 

 simply determine the relative sensitiveness to stimuli of 

 the parts tested. 



To test the power of discriminating between two pres- 

 sure stimuli, the method consists in applying to the surface 

 two points and determining how near together these points 

 can be placed and still felt as two. The relative sensitive- 

 ness of different areas of the body to such a test is given in 

 the following table : ^ 



Area 



Distance of Points Apart 



Tip of tongue . 

 Tip of finger 

 Middle of palm 

 Forehead . . . 

 Back of hand . 

 Forearm . . . 

 Chest . . 



Middle of back 



1 . 1 millimeters 



2.3 



8 to 9 millimeters 



22.6 millimeters 



31.6 



40.6 



45. 



07.7 



N.B. In both methods of test the subject is blindfolded, 



