MOTOR FUNCTIONS OF CEREBRAL CORTEX OF CAT 189 



sulcus and over on the adjacent median surface of the hemi- 

 sphere, about 0.5 mm. 



In cats 15 and 16 that portion of the cortex lying on the 

 banks of the crucial sulcus was exposed either by cutting away 

 one bank or by lifting the posterior bank backward. The sur- 

 face thus exposed was in extent approximately one-third the size 

 of the motor area lying on the exposed surface of the hemi- 

 sphere. Stimulation of it gave results which were in every 

 way similar to those obtained by stimulation of the exposed 

 motor area previously described, and the movements, which were 

 elicited, prove this area to be functionally merely an infolding 

 of the cortical surface, for they involve the same body areas as 

 the adjacent surface cortex. In addition there was a particu- 

 larly rich representation for movements of the head and neck, 

 especially for the tongue, lips, jaws, throat and eyes. The 

 number of non-stimulable areas distributed among the stimu- 

 lable areas, in the exploration of these banks, indicates that the 

 results were true stimulations of the motor cells and not due to 

 overflow of current into contiguous tissue. A fuller account of 

 these fields will be given in a subsequent section and will there 

 be illustrated by diagrams. 



AREAS FOR DIFFERENT SEGMENTAL MEASUREMENTS 



Figures 9 to 16 show graphically the distribution of the areas 

 in the brains of the different animals upon which the tests were 

 made; and the composite of localization in those animals on 

 which complete series were obtained is given in figure 4. As 

 has been noted above, the results on other animals, in which 

 the exploration of one hemisphere was thought not to be suffi- 

 ciently complete, are not included, because it is not sure that the 

 results would have been strictly comparable. The results were 

 plotted on diagrams of a size approximately 5 diameters of the 

 original brains and from the enlarged diagrams the illustrations 

 of the present work were reduced. 



In these figures the longitudinal sulcus and the crucial sulcus 

 are represented by heavy black lines, the other fissures by 



