CHAPTER XXVI 



CUTANEOUS SENSATIONS 



Cutaneous sensations ; Pain spots. Explore with an ordinary pin 

 a portion of the skin of the forearm or back of the hand of another 

 person (who should keep his eyes closed), pressing the point firmly 

 here and there, but without penetrating the surface. Notice that 

 whereas at some places the prick is painful, at others no pain is 

 caused, the feeling being either one of touch or pressure or no 

 sensation is produced. 



Warmth spots. Substitute for the pin a steel or copper rod with a 

 smooth blunt point, like a knitting-pin ; the rod may be provided with 

 a wooden handle. Warm the rod by immersing it in water heated to 

 50 C. Explore the skin by drawing the warm point of the style 

 slowly over it. It will be found that the sensation is only one of 

 warmth at certain points, where it is very distinct ; at others it is 

 merely a sensation of touch. 



Cold spots. Repeat after cooling the rod by immersing it in ire- 

 cold water. In this way spots sensitive to cold alone can be picked 

 out : they are not the same as those which are sensitive to warmth. 



The various spots may be mapped out upon a patch of the skin with coloured 

 inks or pencils, and may be tested again later. They are constant in position. 



Touch sensations ; Determination of the relative delicacy of different 

 parts to touch. Take a fine bristle or coarse hair two inches long, and 

 fix it with sealing-wax to a match to serve as a holder (fig. 80). Ex- 

 plore in another person (who is not to see the part which is touched) any 

 part of the skin, determining the spots which are most sensitive to the 

 pressure of the hair. The point of this is to be brought vertically on the 

 skin without lateral movement and pressed down only just enough 'to 

 bend it slightly. By using a number of bristles of different thickness 



a certain rough scale of delicacy of touch on different parts of the body 



100 



