1903.] On the Cerebral Cortex of the Anthropoid Apes. 153 



excitability of the cortex it retires backward in the direction of the 

 central fissure. 



In a similar manner the boundary of the area for any particular 

 movement, may by " Bahnung " be extended beyond its average limit. 

 The special form of movement provoked from a given spot of cortex 

 is thus influenced by the particular forms of movement excited from 

 neighbouring points just antecedently. 



Among movements elicited from the cortex of the "facial" 

 region, we have in two instances seen protrusion of the tongue, 

 succeeded by forcible closure of the jaws following rapidly before 

 retraction had withdrawn the tongue behind the arcades of the teeth ; 

 so that in these instances the tongue was caught by the closure of the 

 teeth. This sequence of movements presents interest, as evidencing 

 that a sequence of movement evoked by excitation of the cortex may 

 exhibit in some respects faulty co-ordination. The movement, is also 

 of interest as a result of direct cortical excitation which harmonises 

 with the biting of the tongue in epileptic seizures. 



Ablation of the facial area of the " motor " region was performed in 

 one individual. A crossed hemiparesis ensued in the lips, cheek, 

 tongue, nasal fold, and lower eyelid (very slight), but not in the upper 

 lid, eyebrow, or frontal region. 



As to the recovery of movement that occurs in a limb rendered 

 paretic by ablation of its cortical area in the "motor" region, we find 

 the following points: If all the area, which when faradised evokes 

 movements of fingers, thumb, and wrist primarily, and not as a later 

 sequel to movements starting elsewhere, be excised, the paretic 

 condition of the hand which ensues is severe, but rapidly diminishes. 

 In a few weeks the hand is again very fairly and freely used. If, then, 

 the whole of the corresponding area in the opposite hemisphere is removed', 

 a similar paresis similarly ensues in the other hand, and runs a similar 

 course ; but this second lesion does not produce, so far as we have been 

 able to discover, the slightest recrudescence of the paresis already 

 recovered from in the first hand. On the contrary, the first hand is 

 almost at once employed more freely and successfully than prior to the 

 second operation, presumably because of greater inducement to use it 

 during the disability existing in the second hand. If, then, later, 

 after the second hand has regained its use, the remaining part of the 

 arm area first operated upon be ablated, this causes no obvious 

 recrudescence of paresis either in the first hand or in the second hand. 

 It causes severe paresis at shoulder, and to some extent at elbow, 

 on the side crossed to the lesion, but this, again, is in great part 

 of temporary character, and is largely recovered from. In accord 

 with the absence of recrudescence of the hand paresis on ablating in 

 the third operation the remaining intact part of the arm area, we 

 found that faradisation of that part (elbow and shoulder) provoked, as 



