The Kxfitable Corti'X ol' tlu* ("liiinpanzpc. Onm^^-l'taii. and ( iorilla 14.S 



thr points is short, e.g. less than o nun., it is sometimes double or tfeble 

 that. It is not ec|ually developed in all directions, thus it tentls to oceui- 

 more readilv l)etween two |)oints situate in «)ne and th»' same functional 

 area. e.g. leg area, than between two points situate in ditlerent functional 

 area, e.or. one in lei: area and one in arm area. it .seems to occur more 

 readily between points whicii undei- stimulation give rise, in the 'march" 

 (Hughliiigs Jackson) elieitable from them, to similar motor responses. 

 Thus in the march elieitable from "abdominal wall' points movement of anus 

 is prone to occur, and, vice versa, in tlie march tdicitable from " anus points 

 there is a proneness for al)dominal w^ill response to appear: and similarly 

 between anus points and abdominal wall points, though their foci are situate 

 (juite far one from the other, we have seen deviation of response exerted. 



Again, in an experiment a portion of the leg area was al)lated, leaving 

 below the ablated portion a sn)all transverse slip of cortex which the faradie 

 stimulations prior to the ablation allocated to hip area but abutting upon 

 the abdominal wall area. The whole of tiiis stri[) on l)eing laradised twenty 

 minutes after completion of the ablation yielded no trace of limb movement, 

 but evoked in.stead vigorous contraction of the abdominal wall. Prior to 

 the ablation it had yielded as movement cliieHy Hexion of hip; after the 

 ablation it yielded contractions of the contralateral abdominal wall without 

 any movement of hip. 



Again, in a chimpanzee, at the region of the gyr. cent, anterior, opposite 

 the brachio-facial genu of sulc. centralis, the following was noted. The lower 

 limit of hand area was determined, care being taken to avoid as far as 

 possible deviation of response by near precurrent stimulation of adjacent 

 points. Similarly the upper limit of angle of mouth area was delimited. 

 Then the lower limit of hand area was obtained by stimulation in .serial 

 succession of a number of points descending in order from upper part of 

 arm area downward. The lower border of hand area as thus examined 

 trespassed into face area according to the upward limit of the latter as 

 demarcated previously. The responses of hand given by the liand area 

 points thus trespassing were always similar to the last hand responses 

 obtained from the portion of the hand area above them ; and they were 

 accompanied by " angle of mouth " movement, either simultaneous with 

 them or almost so. Conversely, on determining the upper limit of angle 

 of mouth area by following that area upward along a series of points 

 stimulated in it in turn, the upper limit trespassed over into hand area. 

 The responses of mouth movement from these trespassing points always 

 resembled the mouth responses last obtained from points lower down in 

 mouth area, and were accompanied by movements of hand. Similarly, at 

 lower edge of closure of eyelids area that area could by serial stimulation 

 of it be made to encroach on " angle of mouth " area, which lay lower down 

 and rather posterior to it ; and the upper and posterior edge of closure of 

 eyelids area could be made to encroach over into hand area, which lay 

 above and rather behind it. 



VOL. XI., xo. 2. — 1917. 10 



