THE PHYSIOLOGY OF THE NERVOUS SYSTEM 217 



of acuteness i. e., how near together, expressed in millimetres, may 

 the points be felt as two? 



Place the dividers upon any portion of the subject's hand and 

 test the acuteness of touch; the subject will be able to describe accu- 

 rately where the points touch the surface and the more accurately 

 the more acute the tactile sense as tested in the above manner. 



(2) In a similar way test the acuteness of tactile sensation in the 

 following locations: 



Left fourth finger tip; palmar surface of third, second, and first 

 phalanges; dorsal surface of second and first phalanges. 

 Left hand mid-palm, mid-back. 

 Left wrist flexor surface, extensor surface. 

 Left forearm flexor surface, extensor surface. 

 Left upper arm flexor surface extensor surface. 

 Left scapular region. 



(3) Tabulate results for left and right side in case of Mr. A. 



(4) Tabulate results for left and right side for at least two indi- 

 viduals. 



(5) Make a careful study of the results with a view to answering 

 the following questions, which answers may be formulated in a 

 series of conclusions: 



(a) Do different parts of the same individual possess the same 

 acuteness of tactile sensations? 



(6) Do symmetrically located points in the same individual possess 

 the same acuteness of tactile sensation? 



(c) Is there any appreciable variation of acuteness of tactile 

 sensation in homologous points of different individuals? 



(d) Is there any difference in the acuteness of tactile sensation 

 between the flexor and corresponding extensor surfaces? 



(e) Is there a progressive decrease of acuteness as one passes 

 from tip of finger up along the anterior limb? 



(/) Formulate any other conclusions which may be based upon the 

 observations. 



6. The Temperature Sense. (6) Map out upon the flexor surface 

 of the forearm a 3 cm. square field, dividing it into 100 squares- 

 each 3 mm. square. Draw a similar map on paper. Fill one beaker 

 with chipped ice and water, and another with water at 60 C. Put 

 a spike in each beaker. 



Wrap the cold spike in a towel in order that it may maintain its 

 temperature as long as possible. Place its point gently on one of 

 the squares of the skin map; if it feels cold to the subject make a 

 "c" in the corresponding square of the paper map. Slip the cold 

 point from square to square of the skin, noting those squares which 

 give the sensation of cold and recording same on paper map. 



(7) After finding the cold areas, determine in a similar manner 

 the areas which give a sensation of heat for the warm spike. 



