SPACE 3 



points quite distinctly, and then they gradually approach one 

 another until they fuse. 



How does this come about ? How is this movement of 

 approach so clearly detected ? The sensation of pressure does 

 not alter in the least ; the only thing that does alter is the 

 accuracy with which the skin of the back is able to detect the 

 distance between the two points of pressure. From this we 

 may confidently infer that, as well as sensitiveness to pressure, 

 we also have in our skin a power of localisation. 



The theory developed from such experiments states that 

 we have in our skin outspread nerve-endings which envelop 

 the whole surface of the body ; and these are not, so to speak, 

 focussed on specific stimuli, but respond to every kind of 

 stimulus. The terminal nerve-expansions are distributed in 

 areas which vary quite considerably in size. Each area allows 

 one quality to sound, which imparts a definite local colour 

 to the qualities of touch and temperature. 



The areas are measured by determining the distance apart 

 at which the two compass-points are instantly felt as two ' 

 distinct points of pressure. In this way, it has been shown 

 that the areas are by far the smallest and most numerous in 

 the finger-tips and the tip of the tongue. 



The qualities emanating from these areas are called local ^' 

 signs. Investigation of the local signs proves very difficult, 

 because we have to disregard the specific stimulus that accom- 

 panies them ; this requires great concentration of attention, 

 and it can be done with certainty only at a few places on the 

 skin. I find that when I shut my eyes and gently stroke the 

 small hairs on the back of my hand, this brings best to my 

 consciousness the alteration of the local quality. But merely 

 a light touch on the skin of the thigh gives one some in- 

 sight into the relations of the local signs one to another. 

 They are best compared with the musical scale. Imagine a 

 piano with the keys in seven rows, one above another ; in 



