CEREBRAL LOCALIZATION 



583 



It remains now to locate the distinct motor areas. This has been 

 done on the brain of the monkey by Ferrier, Horsley and others, who 

 have applied their observations as nearly as possible to the human brain. 

 While the divisions now recognized can not be taken as absolute, experi- 

 ments on monkeys have been followed by results so nearly constant, 

 that the most important localizations may be accepted as correct. 



i. The centre for movements of the upper extremities is on the 

 outer surface of the brain and includes the superior portion of the as- 

 cending frontal convolution and nearly all the ascending parietal con- 



Fig. 144. Motor cortical zone (Rolandic area) on the outer surface of the cerebrum (Exner). 



volution, except the very uppermost portion of these convolutions, next 

 the great longitudinal fissure. 



2. The centre for movements of the leg and foot is on the mesial 

 surface of the brain, including the paracentral lobule. 



3. The centre for movements of the trunk and shoulders is mainly 

 on the mesial surface of the brain, in front of the upper part of the 

 centre for the leg and foot. 



4. The centre for movements of the head, eyes and lids is on the 

 outer surface of the brain, including the posterior portion of the first and 

 second frontal convolutions and extending to the mesial surface. 



5. The centre for the muscles of the mouth includes the lower por- 

 tion of the ascending frontal convolution. 



The action of all these motor centres is crossed. 



