Sensory Organs and Intelligence 157 



the dormant intellectual powers of these 

 children were brought into play, and they 

 gradually came to comprehend that external 

 things could be specified by definite symbols 

 or movements made with their fingers, i.e., that 

 it was possible to express their thoughts in 

 manual signs. 



It was the exercise of their sense organs of 

 touch, and the motion of their fingers which 

 brought the inherent power of their association 

 nervous centres into healthy action. 



Passing from the eyes, ears, and the other 

 sensory organs of our bodies, ingoing or 

 afferent fibres may be traced which extend to, 

 and terminate in relation with aggregations of 

 nerve cells known as the sensory cortical 

 centres, located in definite areas of the cerebral 

 hemispheres ; in their passage to these centres 

 the fibres give off branches to the basal ganglia. 

 (See Fig. 14.) The nerve cells forming the 

 sensory centres are brought into relation with 

 motor cortical centres by means of association 

 fibres. From the motor centres fibres extend to 

 the lower brain and spinal cord, and in their 

 passage give off branches to the nuclei of nerves 



