140 DR. C. E. BEEVOR AND MR. V. HORSLEY ON THE EXCITATION OF THE 
The above movements are represented in the ascending frontal gyrus : the next to 
be described are in the ascending parietal gyrus. See fig. 17, Plate 19. 
Of these the first is flexion at square No. 38, the second, adduction at squares 
Nos. 39 and 83. 
As before stated, these movements of the thumb were single and unaccompanied 
by movement of any other joint, although the electrodes were finally kept applied for 
5 seconds, a time more than sufficient in the lower Apes to generate movements in all 
segments of that limb, and probably, these in addition, be followed by others in the 
limb of the same side. See conclusions, p. 149. 
Finally, just as we have seen, extension is represented most anteriorly and 
superiorly, so now by reference to fig. 3, Plate 17, it appears that flexion and 
adduction are placed posteriorly and inferiorly. 
The remarkable individual clearness of these and other movements is discussed on 
pp. 151, 152, 
(18) Movements of the Index Finger. —The index finger is always represented in the 
Bonnet Monkey in the cortex next to the thumb area, and its focus in that animal is 
found to be in the ascending parietal gyrus (see fig. 18). It is therefore of great 
interest, and we may add importance to note that also in the Orang the principal 
(indeed, almost the only) representation of this segment is situated next behind and 
above the thumb area, and in the ascending parietal gyrus, viz., at centres 40, 41, 83. 
The kind of movement produced at each square was the well-known purposive or 
voluntary movement of extension ; the subordinate or associated movement of the 
index is alluded to in the next paragraph. The focus of movement appeared to be at 
40, and the representation diminished towards 41 and 83. At 83 there was also 
observed adduction of tire thumb, but there was no abduction of the index by the 
ahductor indicis as might have perhaps been expected, the finger moved only in 
extension, i.e., in its most highly integrated character. 
(19) Movements of the Fingers, —The fingers (all moving in association) were 
represented in the ascending frontal gyrus at squares 28, 29, 30, i.e., above and 
behind the thumb area. The movement evoked at each was invariably extension, and 
this of a remarkably deliberate character, so that the sequence of the segments 
in action was very clearly demonstrated. Thus the first digit to move was the little 
finger, which completely extended, next the ring finger, and finally, less marked 
extension of the remaining' middle and index fingers. No flexion of the Angers was 
noted to occur. See fig. 19. 
(20) Movements of the ITrist.—We have previously (‘Phil. Trans.,’ 1887, 1888) 
urged that the wrist and elbow should be regarded as joints subordinate in primary 
importance to those of the digits and shoulder. In harmony with this view, we found 
in the Orang that the former was represented only in association, e.g., with extension 
of the fingers, and with the following movements : — 
