150 Instinct and Intelligence 



On referring to Fig. 17 it will be seen that 

 considerable intervals exist between the sensory 

 and motor cortical centres; in the brains of 

 ordinary human beings these spaces are occu- 

 pied by nerve fibres and cells which constitute 



Broca's Convolution 

 or senso- motor 

 speech Cfnlrt. 



FIG. 17. Diagram of left cerebral hemisphere (outer surface) of 



human brain. (From Halliburton 's Handbook of Physiology, 



p. 688.) 



its psychical or association areas. It is in these 

 parts of the cerebrum that energy passing from 

 sensory to motor cortical centres is transmuted 

 into intellectual processes, and in that form 

 stimulates the motor centres which control 



