196 



PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



The Motor Area. The first experiments of Fritsch and Hitzig 

 disclosed the location of a cortical region in the dog which upon 

 stimulation gave definite movements. The later experiments of 

 Ferrier, Schafer, Horsley, and Beevor, particularly upon the apes, 

 gave reason for believing that this motor area surrounds the 

 central sulcus of Rolando and extends inward upon the mesial 

 surface of the cerebrum. Its exact boundaries marked out by 



Eyelid /Closure 



Nose f j" Opening 



cords 



Fig. 87. Location of motor areas in brain of chimpanzee. (Sherrington and Green- 

 baum.) The extent of the motor areas is indicated by stippling; it lies entirely in front 

 of the fissure of Rolando (sulcus centralis). Much of the motor area is hidden in the sulci. 

 The regions marked eyes indicate the areas whose stimulation gives conjugate movements 

 of the eyeballs. It is doubtful, however, whether these represent motor areas proper. 



careful stimulation of the region in monkeys was more or less 

 verified upon man, since in operations upon the brain it was 

 often necessary to stimulate the cortex in order to localize a 

 given motor area. By these means charts have been made 

 showing the cortical area for the musculature of each part of 

 the body. It was found that in general the distribution of 

 the areas lies along the central sulcus of Rolando and follows 

 the order of the cranial and spinal nerves. Within each area 

 smaller centers may be located by careful stimulation; thus, the 

 hand and arm area may be subdivided into centers for the wrist, 

 fingers, thumb, etc. Sherrington and Greenbaum,* making 



*" Reports of the Thompson- Yates and Johnson Laboratories," 4, 351, 

 1902; 5, 55, 1903. Also Ley ton and Sherrington, -"Quarterly Journal of 

 Exp. Physiology," 11, 135, 1917. 



