XXIV.] SKIN AND TOUCH. 25.5 



of pressure. The weight should be placed 

 on the same part of the palm of the hand 

 in each case. 



4. Estimate (in either way) the difference of weight 

 which can be appreciated 



a. When the weights are light, e.g. 1, 2, 3, 4, or 

 5 grms. 



B. When the weights are heavy, e.g. 10, 20, 30, 

 &c., or 100, 200, &c. grins. 



Smaller differences will be appreciated in a than 

 in /3. In fact the difference of weight which 

 can be appreciated bears, roughly speaking, a 

 Constant ratio to the whole weight. 



5. Plunge the- finger int9 mercury, and then draw 

 it out. The sensation will be that of a ring 

 passing down and up the finger, the greatest 

 sensation being where there is the greatest 

 variation of pressure. 



C. Place two equal light weights, one cold the other 

 warm, on the corresponding fingers of the hands; 

 the cold one %vill feel the heavier. 



7. Paint a ring of collodion on the palm of the 

 hand, leaving only a small central space, and 

 attempt to distinguish between the approach of 

 a hot body and gentle contact of a feather. 



8. Place the elbow first in warm water, and then 

 in a mixture of ice and water. There will be a 

 sensation of pain in the fingers and cold in the 



