746 



THE CEREBRAL CORTEX. 



was noticed by Beevor and Horsley — (1) That instead of the excitable 

 sphere of the cortex being continuous, as in the monkey, it is, in the 

 orang, interrupted here and there by spaces from which no effect could 

 be obtained even by strong excitations ; (2) that the amount of cortex 

 which is excitable is relatively smaller in the orang than in the monkey. 

 Thus the first frontal gyrus was found to be inexcitable, and most of the 

 upper part of the ascending parietal. Indeed, with the exception of an 



Fig. 339.—/. Rol.,f. liol.', fissure of Rolando, with well-marked genu; Pr. e.f., pre- 

 central fissure ; /. Sy., fissure of Sylvius ; Intra par. /., intraparietal fissure; 

 Par. occ.f., external parieto-occipital fissure. 1, Both eyes move conjugately to 

 opposite side ; 2, Eyes open, eyes and head to opposite side ; 3, Closure of 

 eyelids, those of opposite side most ; 4, Eversion of lower lip on opposite side ; 

 5, Retraction of opposite angle of mouth ; 6, Rolling in of both lips, also 

 opening of the mouth — this latter movement is obtained a little further back 

 than the former ; 7, Pursing of both lips ; 8, Pouting of both lips ; 9, 

 Elevation of upper lip on opposite side ; 10, Movements of the tongue — 

 these occurred over almost all the facial area ; 11, Twitching of orbicularis 

 oris of opposite side ; 12, Movements of the thumb, generally extension — it 

 will be noticed that these were got at three several spots isolated from one 

 another ; 13, Extension of index finger ; 14, Extension of all the fingers, with 

 pronation or ulnar adduction of wrist ; 15, Flexion of elbow ; 16, Adduction of 

 shoulder ; 17, Area for movements of lower limb. Movements of hallux, small 

 toes, ankle, knee, and hip all occur at various points in this area (which 

 extends over to the mesial surface), but movements of the hip and knee were 

 not got rpiite as high as movements of the toes and ankle, antl, on the other 

 hand, their area of representation extended a little lower ; 18, An outlying spot 

 where extension of toes was obtained. 



area for eye-movements in front of the precentral sulcus, almost the 

 only parts of the fronto-parietal lobe found to be excitable were the 

 ascending frontal gyrus, the lower two-thirds of the ascending parietal 

 gyrus, and the marginal gyrus opposite the upper end of the ascend- 

 ing frontal : (3) the tendency to provoke a sequence or march of 

 movements from stimulation of one point only, which is so often met 

 with in the monkey, is very much less marked in the orang. The 



