260 



THE CUTANEOUS SENSES. 



With a pair of dividers find the least distance at which 

 the points can be distinguished as two separate impressions 

 when they are applied simultaneously to the skin. Measure 

 the intervals with a millimetre scale. 



Test the tip of the tongue, the skin of the lips, forehead, 

 cheeks, hand, forearm, and back of the neck. 



The pain sense. Explore the skin of the hand and forearm 

 with Aly's instrument, which consists of a long needle kept 

 projecting from a sheath by means of a light spring. The 

 pressure which is required to produce a feeling of pain is 



read off in grammes upon the gradua- 

 tions on the sheath. The camel hair 

 brush at the other end of the instru- 

 ment is the common clinical means 

 used to detect diminution of sen- 

 sibility. 



By arming the end of the needle 

 with a small piece of cork it can be 

 used for exploring the pressure sense. 



Use the von Frey human hair for 

 exploring the conjunctiva for the 

 pain sense. 



Hot and cold sense. Use Gold- 

 scheider's metal rods (1 cm thick by 

 9 long). Explore the back of the 

 hand and forearm by touching the 

 surface lightly with the tip of the rod. 



First explore for spots, which at 

 once respond by a feeling of cold. 



The metal is usually cold enough 

 at ordinary temperatures, and need 



FICI. 56. Aly's .-Esthesiometer. 



not therefore be specially cooled. 



