282 PHYSIOLOGY. 



very close together, they will be/>// as one pressure. That 

 part which can best distinguish, as two points of touch, 

 these blunt points, is considered the most sensitive. By 

 this test the tip of the tongue is the most sensitive, being 

 able to distinguish, as two separate points of contact, the 

 tips of the compasses when only one twenty-fifth part of 

 an inch apart. Following is the order of degrees of sen- 

 sitiveness : tip of tongue, tips of fingers, lip, tip of nose, 

 eyelid, cheek, forehead, knee, neck; while the middle of 

 the back seems least sensitive, the two points not produc- 

 ing two distinct sensations until they are more than two 

 and a half inches apart. In general those parts which are 

 most used, and those parts which are more freely movable, 

 are most sensitive ; for instance, the knee is much more 

 sensitive than the middle of the thigh or the middle of the 

 leg, and the elbow than the middle of the arm or forearm. 

 If the compass points, about half an inch apart, be passed 

 from the palm to the tips of the fingers, it will at first seem 

 one line gradually separating into two diverging ones, 

 owing to the keener localizing power as the finger tips are 

 approached. 



Reference of Sensation to the Region of Nerve End- 

 ings. If the "funny bone," or "crazy bone," be hit, i.e. 

 if the ulnar nerve be bruised against the bone, sharp pain 

 may be felt in the wrist and hand, and soreness of these 

 parts may be felt for days, though they are not in the 

 least injured, but only the nerve at the elbow. The cur- 

 rents along this nerve rouse sensation that we have learned 

 to localize at the endings of the nerve fibers. So, too, 

 after amputation of a hand or foot, there may for years 

 be sensations referred to the missing member, probably 

 due to irritation of the nerves of the stump. There is, 



