XVI 



THE NERVOUS SYSTEM 



233 



FlG. 127. Outer surface of the right hemisphere. 

 The dots indicate the sensory, the lines the 

 motor, and the clear spaces the association 

 areas. (Modified from Flechsig by Pratt.) 



and doubtless have some important function. It is now 



believed by some scientists that the three association 



areas are thought 



centers. The sen- 

 sory impressions, 



it is claimed, are 



carried from the 



sensory areas to 



the association 



areas, and from 



them to the motor 



area by means of 



nerve fibers which 



connect these 



parts with each other. These association areas may be 



the centers for memory, imagination, and judgment. 



All this, however, 

 is largely theoreti- 

 cal at present. 



The brain has 

 three kinds of 

 nerve fibers. First, 

 those that carry 

 impressions up 

 from the spinal 

 cord to the sensory 

 areas, and down 

 from the motor 



areas ; they are called projection fibers. Second, those 



that connect different parts of the two hemispheres with 



FlG. 128. Inner surface of the left hemisphere. 

 The dots indicate the sensory, the lines the 

 motor, and the clear spaces the association 

 areas. (Modified from Flechsig by Pratt.) 



