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n. What Differences of Pressure can be distinguished ? 



METHOD. One student lays his hand on the table, palm 

 upwards. He keeps his eyes closed while another student 

 applies to the palmar aspect of the proximal phalanx of the 

 middle finger the different weights supplied. The weights 

 must be applied to the same place in the same way each 

 time, and at as nearly as possible equal intervals of time. 

 They must be left on for the same time. As each weight is 

 applied the subject of the experiment says, " the same," unless 

 he is sure that there is a difference, in which case he says 

 " heavier " or " lighter." 



Recording the result of each observation, the experimenter 

 then calculates and records the smallest percentage differ- 

 ence of weight which can be appreciated with certainty. 



III. Can Points of Contact be discriminated equally well at 



different Parts of the Surface ? 



METHOD. This may be determined by finding how near 

 to one another two contacts may be made and felt as two 

 and not simply as one contact. 



One student closes his eyes and lays his hand, palm down- 

 wards, on the table. The experimenter then takes a pair of 

 compasses, and, holding them loosely in the hand with the 

 points somewhat separated from one another, he lightly brings 

 either one point or the two points simultaneously down 

 upon the back of the subject's hand. The subject must say 

 " one " unless he is certain that he feels two points of contact. 

 Working in this way, and recording the result of each observa- 

 tion as to the distance of the points and the resulting sensa- 

 tion, the experimenter determines and records how far the 

 points must be apart on the back of the hand to give rise with 

 certainty to a double sensation. 



The observation is next to be repeated on the palmar aspect 

 of the terminal phalanx of the forefinger. 



IV. Can Contacts be distinguished however rapidly they follow 



one another ? 



METHOD. Place the finger upon the toothed wheel first 

 when it is rotating slowly and then when it is rotating rapidly, 



