254 ELEMENTARY PHYSIOLOGY. [XXIV. 



B. Touch. 



1. Power of localisation. 



Using a pair of small bone or wooden compasses, 

 determme the distance at which the points must 

 be placed from each other in order that they 

 may be felt as two points when applied lightly 

 and with the same force to various parts of the 

 body. Try if the following order is correct : tip 

 of tongue, tips of fingers, palm of hand, cheeks, 

 back of hand, fore-head, front of fore-arm, back 

 of fore-arm, back of neck, &c. 



2. Sensation of temperature. 



Dip a small metallic knob in hot water {e.g. 

 70° C), and applying it to the same parts of the 

 body as before, determine roughly the sensitive- 

 ness to temperature of these parts. 



S. Estimation of weight. The muscular sense. 



a. Determine the smallest difference in weight 

 which can be appreciated when slightly 

 differing weights are held in the palm of 

 the hand. 



h. Then laying the hand and arm supine on a 

 table, so that they are motionless, and placing 

 weights on the palm of hand, determine as 

 before the difference of weight which can be 

 appreciated. This will be much less in the 

 case of (6) than of (a). In (a) the muscular 

 sense is employed; in (&), only the sensation 



