SENSITIVENESS 195 



Millimetres. 



Lower third of the forearm, volar surface 15 



Tn front of the zygoma 15-8 



Plantar surface of the great toe 15-8 



Inner surface of the lip 20-3 



Behind the zygoma 22-6 



Forehead, - 22-6 



Occiput 27-1 



Back of the hand 29-8 



Under the chin - 33-8 



Vertex 33-8 



Knee - 36-1 



Sacrum, gluteal region 44-6 



Forearm and leg 45-1 



Neck - - 54-1 



Back of the fifth dorsal vertebra ; lower dorsal 



and lumbar region 54-1 



Upper arm ; thigh ; centre of back 67-7 



.Middle of the neck 67-7 



The intensity of the contact sensation is increased in a mechani- 

 cal way by the presence of hairs, because they act as levers on the 

 tactile corpuscles. The whiskers of the cat render the touch 

 points of the jaw very sensitive in this way, being able to detect 

 even slight air currents. 



Absolute sensitiveness as indicated by a sense of pressure is 

 generally determined by finding a minimum pressure necessary 

 to evoke a minimal sensation. Below is given the weight in 

 grams which could just be detected when placed on various parts 

 of the skin. The values given are normal values (Table XXX.). 

 Practice may increase the discriminating point. Every one 

 knows how a blind man " sees " with his fingers. 



TABLE XXX. 



Tongue and nose 2 



Lips - 2-5 



Finger-tip and forehead - 3 



Back of the finger 5 



Palm of the hand, arm and thigh 7 



Forearm 8 



Back of the hand - 12 



Back of the leg and shoulder - 16 



Abdomen 26 



Sole of the feet 28 



Back of the forearm 33 



Gluteal region 48 



In a similar way one could map out the hot and cold spots and 

 the pain spots in the skin. They vary in distribution but not in 



