THE PERCEPTION OF SPACE. 161 



sensibility is touched, to move the member so that the 

 touching object glides along it to the place where sensi- 

 bility is greatest. If a body touches our hand we move the 

 hand over it till the finger-tips are able to explore it. If 

 the sole of our foot touches anything we bring it towards 

 the toes, and so forth. There thus arise lines of habitual 

 passage from all points of a member to its sensitive tip. 

 These are the lines most readily recalled when any point 

 is touched, and their recall is identical with the conscious- 

 ness of the distance of the touched point from the ' tip.' I 

 think anyone must be aware when he touches a point of 

 his hand or wrist that it is the relation to the finger-tips of 

 which he is usually most conscious. Points on the fore- 

 arm suggest either the finger-tips or the elbow (the latter 

 being a spot of greater sensibility*). In the foot it is the 

 toes, and so on. A point can only be cognized in its rela- 

 tions to the entire body at once by awakening a visual 

 image of the whole body. Such awakening is even more 

 obviously than the previously considered cases a matter of 

 pure association. 



This leads us to the eye. On the retina the fovea and the 

 yellow spot about it form a focus of exquisite sensibility, 

 towards which every impression falling on an outlying por- 

 tion of the field is moved by an instinctive action of the 

 muscles of the eyeball. Few persons, until their attention 

 is called to the fact, are aware how almost impossible it is 

 to keep a conspicuous visible object in the margin of the 

 field of view. The moment volition is relaxed we find that 

 without our knowing it our eyes have turned so as to bring 

 it to the centre. This is why most persons are unable to 

 keep the eyes steadily converged upon a point in space with 

 nothing in it. The objects against the walls of the room 



* It is true that the inside of the fore- arm, though its discriminative 

 sensibility is often less than that of the outside, usually rises very promi- 

 nently into consciousness when the latter is touched. Its (esthetic sensi- 

 bility to contact is a good deal liner. We enjoy stroking it from the ex- 

 tensor to the flexor surface around the ulnar side more than in the reverse 

 direction. Pronatiug movements give rise to contacts in this order, and 

 are frequently indulged in when the back of the fore-arm feels an object 

 uiraiust it. 



