THE PERCEPTION OF THINGS. 105 



down by Eeid and Helmholtz that true sensations can 

 never be changed by the suggestions of experience. 



A certain illusion of which I have not yet spoken affords 

 an additional illustration of this. When ive loill to execute a 

 movement and the movement for some reason does not occur, 

 unless the sensation of the parfs not moving is a strong one, ive 

 are apt to feel as if the movement had actually taken place. 

 This seems habitually to be the case in anaesthesia of the 

 moving parts. Close the patient's eyes, hold his anaesthetic 

 arm still, and tell him to raise his hand to his head ; and 

 when he opens his eyes he will be astonished to find that 

 the movement has not taken place. All reports of anaesthetic 

 cases seem to mention this illusion. Sternberg who wrote on 

 the subject in 1885,* lays it down as a law that the intention 

 to move is the same thing as the feeling of the motion. We 

 shall later see that this is false (Chapter XXV) ; but it 

 certainly may suggest the feeling of the motion with hallu- 

 cinatory intensity. Sternberg gives the following experi- 

 ment, which I find succeeds with at least half of those who 

 try it : Rest your palm on the edge of the table with your 

 forefinger hanging over in a position of extreme flexion, 

 and then exert your will to flex it still more. The position 

 of the other fingers makes this impossible, and yet if we do 

 not look to see the finger, we think we feel it move. He 

 quotes from Exner a similar experiment with the jaws : Put 

 some hard rubber or other unindentable obstacle between 



* In the Proceedings of the AraericHn Society for Psychical Research, pp. 

 253-4. I have tried to account for some of the variations in this conscious- 

 ness. Out of 140 persons whom I found to feel their lost foot, some did so 

 dubiously. "Either they only feel it occasionally, or only when it pains 

 them, or only when they try to move it; or thej' only feel it when they 

 ' think a good deal about it ' and make an effort to conjure it up. When 

 they 'grow inattentive,' the feeling 'flies back' or 'jumps back,' to the 

 stump. Every degree of consciousness, from complete and permanent hal- 

 lucination down to something hardly distinguishable from ordinary fancy, 

 seems represented in the sense of the missing extremity which these 

 patients say they have. Indeed I have seldom seen a more plausible lot of 

 evidence for the view that imagination and sensation are but differences of 

 vividness in an identical process than these confessions, taking them alto- 

 gether, contain. Many patients say they can hardly tell whether they 

 feel or fancy the limb. " 



