MOTOR CORTEX AND INTERNAL CAPSULE IN AN ORANG-OUTANG. 139 
In this movement the tongue appeared to be adjusted horizontally to the floor of 
the mouth, while the upper surface of the opposite half, was slightly hollowed (see 
fig. 16) and its tip retracted from the teeth. 
Movements of the Upper Limb. 
Proceeding now to investigate the mode of representation of the limbs, we will 
commence with that of the upper limb, taking the segments in order from below 
upwards, beginning with the thumb. But we cannot forbear from pointing out that 
it will be seen, especially now, how extremely integrated is the representation in this 
animal, and in the case of the upper limb we actually found it quite exceptional, with 
a minimal stimulus, for more than one segment to be represented at any given point. 
Further, owing to the exaggeration of the bend of the ascending gyri above the 
genu of the Fissure of Rolando, the foci of the segments of the upper limb are 
arranged along a curved line which is horizontal at its lowest point and becomes 
vertical where the limb areas are contiguous, whereas, in the Bojniet Monkey, as we 
have shown, the foci are arranged in a straight but oblique line, parallel to the 
Fissure of Rolando. The functional arrangement and sequence of the representa¬ 
tion of the segments being the same in the two animals, we think it is clear that this 
difference in horizontal level is simply due to the extreme bending of the Fissure of 
Rolando in the Orang. In illustration of this we show, in fig. 4, p. 150, the curve 
of the Fissure of Pv-OLANDO in the two animals, with words indicating the foci of the 
segmental representation. 
(17) Movements of the Thumb .—We observed the thumb to execute the following 
simple movements at the points indicated. 
Action. 
Square. 
Flexion. 
.38 
Adduction, flexion .... 
3.5, 36, 36' 
Adduction. 
39, 83 
Extension. 
37, 37', 138 
We now have to point out the arrangement of the respective order of representa¬ 
tion of these movements, and we shall compare that order with the simpler order, as 
seen in the Bonnet Monkey. 
Thus, to begin :—Extension of the thumb we see is represented at 37 and 37', i.c., 
in the foremost part of the area of representation. Now this is exactly the localisa¬ 
tion we have demonstrated to occur in the Bonnet Monkey. 
With a stronger current (8’5 cm.) we once obtained extension of the thumb at 138, 
which is, of course at the opposite pole of the thumb area. 
The movement represented next to extension is that of adduction-flexion at 
squares 35, 36, 36'. 
