COORDINATION AND CONTROL: (1) THE NERVOUS SYSTEM 



123 



CEREBRAL CORTEX 



sensory receptor SPINAL CORD 



Fig. 7.11. The mechanism of third-level response, superimposed on those of the first and 

 second levels, (a) Axon; (d) dendrite. (Modified from Gates, Elementary Psychology, by per- 

 mission The Macmillan Company.) 



It is the supreme governing agency of the nervous system and is capable 

 of interfering with and modifying the activities of the lower centers. 



The cerebrum, or forebrain, is a fissured and convoluted mass, com- 

 posed of two hemispheres. Its weight is more than four-fifths of the total 



