202 Leyton and Sherrington 



The eyelid-closure area was then carefully ablated within the delimita- 

 tions marked in the map (fig. 12, B). The dura was replaced, stitched, and 

 the whole wound closed with aseptic precautions. On recovering from the 

 operative narcosis the animal was noticed not to close the eyelids fully 

 when blinking. Blinking was as frequent apparently as usual, and could 

 be elicited by suddenly approaching the hand to the animal's face. 

 Stronger eyelid-closure was elicited by touching the eyelids or conjunctiva, 

 but even then the eye-closure was not tight, and seemed distinctly less 

 vigorous than normal. The eyelid-closures which the animal now showed 

 were clearly much less tight and vigorous than had been the closures 

 evoked by many of the stimulations applied to the cortex. In these latter 

 the skin of the eyelids themselves often was actually wrinkled by the 

 closure, but this was never the case now with the closures produced by 

 the animal itself, even in response to touching the conjunctiva. 



The next day the condition remained the same as regards eyes. Some 

 paresis of the lips was obvious. 



December 8. — "The closing of the eyes seems now better; paresis in 

 face quite as marked as yesterday ; wound puffy." 



It was then determined to open up the cortex ; this was done under 

 deep anesthesia. The whole of the central region of both hemispheres 

 was then systematically examined b}* unipolar faradisation. Nowhere in 

 either precentralis were any further points found yielding eye-closure. 

 The eye-closure area of both sides appeared to have been completely 

 extirpated. The " motor " area otherwise gave under the analysis results 

 in harmony with the results obtained on the two previous gorillas. The 

 results were mapped and recorded, but as the observations on the other 

 two animals have been given in some detail, and these on this animal 

 presented no obvious departure from those, the details are not reproduced,, 

 although incorporated in the general list of movements recorded in the 

 anthropoids examined by us. 



Ablation-Experiment 6. Removal of major part of left 

 Gyrus centralis anterior (fig. 26). 



Troglodytes niger, ^ , very young, weight 2*45 kilog., well nourished ; 

 takes milk, sucking it from bottle. 



July 27. — Left hemisphere exposed under deep anaesthesia; full aseptic 

 procedure ; the centralis region laid bare for its whole length ; gyri centrales 

 anterior and posterior explored by faradisation ; no responses evoked from 

 post-centralis anywhere, but precentralis offered a seemingly continuous 

 field of excitable points throughout its whole length. The mesial face of 

 hemisphere was not explored. Protrusion of anus was evoked from 

 extreme top of centralis anterior well in front of upper end of central 

 fissure. Coming down the length of gyrus precentralis the general results 

 were like those obtained in other specimens. The abdomen-chest area 

 between leg field and arm field was well evident, there being no spur 



