ORIGIN OF PHYSICAL CONCEPTS 31 



+ we are told, largely employ the feet in walking 

 as a source of locative data. 



To the concepts reached by such palpation with 

 the hand, M. Villey gives the name of Manual 

 Space. In this connection he thinks it necessary 

 to distinguish between synthetic touch and analytic 

 touch the former resulting from the simultaneous 

 application of different parts of the hand on the 

 surface of a body, the latter that which we owe 

 to the movements of our fingers when having only 

 one point of contact with the object the fingers 

 follow its contour. Various examples of the 

 delicacy of the information thus obtainable are 

 given. Following two straight lines with the thumb 

 and index respectively, a blind man can acquire by 

 practice a sensibility so complete as to enable him to 

 detect the slightest divergence from parallelism. 



The analysis passes on from the data of Space 

 manual to those of Space brachial ; then to the infor- 

 mation derived from walking and other movements 

 of the lower limbs, and then to the co-ordination of 

 the information derived from the sensations of hear- 

 ing, which is necessarily very important to the blind. 



The conclusion of the whole matter is that our 

 principal spatial ideas are common alike to the 

 blind and the vident. Both can be taught and are 

 taught the same geometry. Both understand one 



