30 



possible to move the weight, then study the record of the 

 onset of fatigue upon the drum. Compare your record with 

 those of others. 



The trace upon the drum must not be looked at during the 

 experiment. 



* 



V. RECEPTOR MECHANISMS THE SENSES. 



How do different External Conditions act upon the 

 Body? 



Sensations, changes in the condition of consciousness, are 

 largely used in the study of these questions, and the precautions 

 required for such psychological methods must be observed. 

 The element of expectancy is apt to interfere with the relia- 

 bility of the observations. 



/. CONTACT WITH GROSS MATTER. TOUCH. 



With the eyes shut, touch any object, e.g. the table, and 

 try to formulate all that you can learn about it through the 

 sense of touch. 



Hardness or softness how determined ? 



Roughness or smoothness how determined ? 



Temperature how determined ? 



I. Is Contact felt equally all over the Surface ? 



METHOD. (1) Fit two or three brush bristles of different 

 strengths into split wooden matches. One student now lays 

 his hand on the table, palm downwards, and closes his eyes. 

 The other touches various points close together over a small 

 part of the back of the hand, about | inch square, and the 

 student experimented upon says whether he feels the contact 

 or not. The points on which contacts are most clearly felt 

 are mapped out (Pressure Spots). By more firm pressure 

 Pain Spots may also be discovered and mapped. 



(2) Holding a small fragment of soft cotton wool in the 

 hand, pass it lightly over different areas of skin, and note the 

 sensation produced, and whether all parts are equally 

 sensitive. 



