GENERAL PHYSIOLOGY OF THE CEREBRUM. 



195 



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 



Toes 

 Ankle ^^ 

 Xnec 

 Hip-. 



J'inyers 



y/ A&aiis Abdomen^ 



Eyelid /Closure \ ^^ \ L '"^'^Z ^Suleus Centralis 



Nose ^J'''*' Obening Voea,!. Mastieatro^ 

 oHaio cords 



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

 baum.') The extent of the motor areas is indicated by stippHng; 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. 



use of electrical stimulation, unipolar method, have explored 

 carefully the motor areas in the monkey. They state that 

 these areas do not extend back of the central sulcus, but lie 

 chiefly along the anterior central convolution, as represented 

 in Figs. 87 and 88, and extend for only a small distance on to 

 the mesial surface of the cerebrum. The area thus delimited 

 by physiological experiments is the region from which arises 

 the pyramidal system of fibers, and clinical experience has 



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

 1902; 5, 55, 1903. Also Leyton and Sherrington, "Quarterly Journal of 

 Exp. Physiology," 11, 135, 1917. 



