176 Ley ton and Sherrington 



Knee. — Extension, of knee as the sole movement of a response is rare, 

 much more so than is flexion. 



Ankle. — Movement of ankle occurs often as a leading movement, but 

 tends to be rapidly followed by movement of some other part of the limb. 



Dibits. — Isolated movement of individual digits is not uncommon, as 

 the " list of movements " shows. Some of the movements obtained from 

 cortical stimulation of the anthropoid are such as we find difficult of 

 execution ourselves. This was notably so with the foot area. Flexion of 

 dio-its alono; with dorsal flexion of ankle we observed under cortical stimu- 

 lation both in chimpanzee and orang. Extension of the 2nd toe isolatedly 

 from the other toes was also seen. 



6. Perineum Area, 



Anal movement, usually protrusion, was elicitable fairly regularly and 

 readily from a small area near the mesial border of the hemisphere in the 

 anterior part of leg area, and apparently surrounded by this latter. The 

 movement often seemed bilaterally symmetrical, but with weak stimuli was 

 usually quite clearly unilateral and contralateral. Associated with it secon- 

 darily was movement of abdominal wall, as has been noted in the smaller 

 monkeys by Schafer (36) and by Jolly and Simpson (22). 



Inferences regarding Functions of the Motor Cortex. 



Franz (17) has recently obtained experimental evidence indicating that 

 the functional topography of the motor cortex exhibits inMacacus rhesus 

 demonstrable variation from individual to individual. The larger scale on 

 which the motor cortex presents itself in the anthropoid, and the greater 

 degree to which isolated movements of separate motor parts are elicitable 

 from it, favours examination of the question, although our observations 

 were not specially directed toward it when they were made. Compared 

 one with another, the charts obtained from our anthropoid specimens of 

 the same species exhibit, as said above, differences in detail ; the amount 

 of difference varies very greatly, as reference to those of the charts re- 

 produced will show. The differences are present even in those brains 

 in which the convolutional pattern is less dissimilar than usual, and are 

 then for that reason better recognisable. One difficulty for such com- 

 parisons is the fluctuating character of the sulci as landmarks for evaluat- 

 ing the topography. Since we must suppose that the sulci have some 

 functional significance, this fluctuation may itself be taken as an indication 

 of individual variation of function. And certainly variation of convolu- 

 tional pattern from individual to individual is, in our experience, one of the 

 most salient structural features of the anthropoid cerebrum. Another 

 difficulty in making the comparison from individual to individual is the 

 fact, illustrated above, that the cortical motor points, or many of them, 

 are within limits functionally unstable. The chart obtained from a motor 



