MOTOR FUNCTIONS OF CEREBRAL CORTEX OF CAT 225 



tion of the various points in the area for control of these latter 

 movements give bilateral movements which are well coordinated 

 and purposeful in nature. A similar result is found from scat- 

 tered stimulations from various places controlling movements 

 of the limbs. 



6. The area outside of the fissura coronalis is practically barren 

 of results from stimulation. 



Banks of the sulci cruciales. 7. The anterior and posterior 

 banks of the crucial sulci give reactions which are not quite so 

 widespread over the body musculature as are those from stimu- 

 lation of the surfaces of the hemispheres, but which are coor- 

 dinated equally as well for those members which they do involve. 

 The anterior bank controls movements of the tongue, mouth, 

 throat, neck, eyes, pupils and fore feet. The posterior bank 

 controls movements of the tongue, mouth, eyes, face and ears 

 and fore and hind limbs. 



Variability of motor control. 8. Analysis of the results from 

 stimulation of the cortices of cats 8, 9, 10, 11, 12, 14, and 15 as to 

 the types of movement included in the responses indicates a con- 

 siderable degree of complexity in the cortical representations for 

 the activities of the muscles. When analysed into their simpler 

 component parts it is found that the average response to each 

 stimulation applied to the right cortex included 1.99 simple move- 

 ments, and of the left cortex 1.95 simple movements. This is 

 subject to considerable variation in the individual animals, as 

 shown by the results for cat 8, right hemisphere, of 2.79 and for 

 cat 10, left hemisphere, of 1.36 movements per stimulation. 

 It is subject to considerable variation even in the responses 

 from the two hemispheres of the same animal, as shown in the 

 case of cat 10. The average number of simple movements per 

 stimulation of the right cortex of this animal was 1.85; and 1.36 

 for the left cortex. 



9. Comparison of the frequency of the various types of move- 

 ments of the joints of the limbs indicates that on the right side 

 an average of 82 per cent and on the left side an average of 86 

 per cent of the total cortical responses were movements of some 

 type of the joints of either fore or hind limb. As to the relative 



PSYCHOBIOLOGY, VOL. I, NO. 3 



