The Excitable Cortex of the Chimpanzee, ()rani,^-Utan, and (Jorilhi 201 



The nioveujent of openinf^ of eye responsive to faradisation of frontal 

 cortex anturior to precontralis occurred, as mentioned above, in relation to 

 two seemingly separable tields. (Jf these the lower one {i\^. 12, A) lay with 

 sulcus precentralis inferior not far behind it. From this region the scattered 

 points evoked eye-openinij, often (juickly followed by lateral deviation of 

 the pupils towards the contralateral side. Tiie other and higher field lay 

 with the superior spur of sulcus precentralis medius Ix-hind it, and the 

 inferior spur of sulcus precentralis superior farther behind it .still. In this 

 upper held the scattered points yielded eye-opening seemingly secondarily 

 to turning of the eyeballs to contralateral side. 



After the exposed region of cortex had been carefully explored and 

 these results noted and mapped, the whole of the small field yielding eye- 

 closure was carefully excised, the limits of the excision being shown in the 

 map (fig. 12, A) by a dotted line. 



The dura was then replaced, stitched, and the whole wound closed. 

 On recovering from the operative narcosis the animal revealed no indica- 

 tion whatever, so far as could be detected, of this lesion in regard to the 

 eyes or eyelids. There was, however, distinct, though slight, drawing of 

 the mouth toward the left side, and a slight flattening of the nasal fold on 

 the right side, i.e. some slight paresis of lower part of face on right side. 

 These symptoms were obvious the same evening and the next morning, 

 and no others were observable. Two days later the slight facial paresis 

 was no longer observable, and no abnormality of eyelids had been noted 

 at any time. 



December 6. — Under deep chloroform narcosis trephined over the 

 lower centralis region of right hemisphere. Centralis fissure exposed from 

 genu superius downward, also the frontal region anterior to it for some 

 distance. Precentralis carefully explored with unipolar faradisation, with 

 especial reference to eyelid-closure area. . A small continuous field of excit- 

 able points giving this movement as its primary response was made out, as 

 indicated on map (fig. 12, B). Precentralis above and below also ofiered a 

 seemingly continuous field of motor points ; characteristic landmark points 

 in the field as noted among others at the time are inserted in the map. It 

 was noted that the eye-closure obtained from precentralis seemed rather 

 more markedly contralateral than usual, i.e. that the associated closure of 

 right eye accompanying closure of left seemed rather weaker than usual. 

 As with the left hemisphere explored five days previously, so here with the 

 right, a wide field yielding eye-opening was met with, and this field seemed 

 separable into a lower and an upper, as in the left hemisphere, and the 

 characters of its reaction resembled those already mentioned for the corre- 

 sponding area of left hemisphere. It was noted, however, that from two 

 points in the lower field the movement of eye-opening was followed by 

 distinct convergence of the eyeballs, the convergence being directed toward 

 a point not far aside from a plane continuous with mid-sagittal plane 

 of head. 



