1002 A MANUAL OF PHYSIOLOGY 



pricking. Especially compare the result of stimulating the region 

 in the immediate neighbourhood of the hairs with the spaces between 

 hairs. Discriminate the touch sensation given by the light contact 

 of the pin-point from the painful impression caused when the 

 pressure is increased. Note that the touch element is more evanes- 

 cent than the pain element. 



(2) With strong v. Frey hairs determine the pressure at which 

 the sensation of touch passes into that of pain. 



(3) Compare the sensibility to pin-pricks of the mucous membrane 

 within the mouth with that of the skin. 



