EXERCISE 88 



The sensitiveness of living things depends upon the irritability of protoplasm ; but the sensitive- 

 ness of a particular organ or area of a many-celled animal depends upon the distribution of special 

 nerve-endings in that part. 



Problem. Are some parts of the body surface more sensitive to touch than other parts ? 



What to use. Two students working together ; a pair of dividers ; a ruler. 



What to do. Open dividers about an inch. With the subject blindfolded, apply the two points at 

 the same time on some part of the skin surface, and again but one point. The subject is to tell whether 

 one or two points have been touched. Proceed in this way, opening or closing the dividers as needed, 

 until you know the shortest distance that can be distinguished as two separate points. Repeat oil 

 different parts of the body. 



Record. Tell the smallest separation between two points that you and your partner can distinguish 

 by touch in the various regions, using millimeter or sixteenth of an inch as unit. 



Questions. 1. Of what practical significance are the differences among the various regions? 



2. Of what practical significance are the differences among various people ? 



3. What other differences may there be between people as to the sense of touch ? 



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