222 INITIATIVE IN EVOLUTION 



Skin Region. 

 Forearm and leg 

 Dorsal surface of foot 

 Surface on outer border 



sternum 

 Back of neck 

 Middle of back 

 Upper arm and thigh 



Table VII. — (According to Weber's Law.) Average differences in 



different regions of skin of sensation of pressure. 



Forehead 



Lips 



Dorsum of tongue ) ¥ X o to ^V 



Cheeks 



Temple 



Finger nail 



Dorsal surface of forearm, leg, 



and thigh 



Dorsal surface of hand 



i +/-> i 



Dorsal surface of 1st and 2nd^s T V to 



•2 



phalanges of fingers 

 Palmar surface of finger 

 Palmar surface of hand 

 Flexor surface of forearm 

 Dorsum of foot 

 Dorsal surface of toes 



Plantar surface of toes \ More than ^ 



Sole of foot 



Surface of leg and thigh 

 Thus on the forehead differences of pressure are distinguished 

 when they are increased by -— , whereas on the dorsum of 

 the foot they have to be increased by T V to be distinguished . 

 This is carried out by impact of little balls of a light 

 substances such as pith. 



It may be remarked of these tabulated results that on the 

 one hand they are the results of work extending over some seventy 

 years and numerous observers, and on the other that, broadly 

 looked at, they all tell the same story of stimuli in their incidence 

 on the skin — those of pain, cold, warmth and touch. There is 

 also one thread of origin running through all, and that is that the 

 regions most exposed to the four stimuli show the highest develop- 

 ment of specialised function and structure. 



