104 EXPERIMENTAL PHYSIOLOGY 



LXVI. — Cutaneous Sensations. 



Apparatus. — A pair of metal . compasses, toothpicks, a dish of 

 boiUng water, a dish of ice water, pen and ink. 



Directions. — One pupil should operate, another acting 

 as subject. The subject should be blindfolded. 



A, Touch, Sharpen the ends of the toothpicks and tie 

 one to each arm of the compass. What is the least distance 

 apart at which the two points may be held and felt as two 

 points, when applied to the tips of the fingers? the tip of the 

 tongue? back of the hand? forearm? back of the neck? 

 Record the results. Are all parts of the body equally 

 sensitive to touch? Which parts are most sensitive? 



B, Temperature. Dip a metal point of the compasses in 

 cold water and move it lightly over the back of the hand. 

 Does it feel equally cold to all parts of the skin? Mark 

 with an ink dot those points where the sensation is most acute. 

 Now dip the metal point in the hot water and move it over 

 the same area. Locate, as before, the spots where sensation 

 is most acute. Do the hot and cold spots coincide? What 

 do you conclude about the temperature sensation power 

 of the skin? Is it a general or a localized sensitive power? 

 Test other areas of the body in the same way. Are the 

 temperature spots equally numerous in all parts? Where 

 are they most numerous? least numerous? 



LXVII. — Study of the Tongue. 



Directions. — Protrude the tongue as far as possible and 

 with the aid of a mirror examine its surface. Note the 

 raised points (the papillce) on the surface. Observe that 

 they are of three forms: long and slender (filiform) j mush- 



