160 
DR. C. E. BEEVOR AND PROFESSOR Y. HORSLEY ON A 
half of the area. Indeed, a glance at Table 3 will show that it is almost the only 
movement in the lower third of the area, in which portion of the cortex, too, the joint 
is very feebly represented, movement of it only being met with once in ten times on 
stimulating the centre 5'. (See fig. 2 and Table 3.) 
Adduction is the characteristic movement of the shoulder “ centres ” in the 
ascending parietal gyrus. Retraction (i.e., extension with rotation out and some 
adduction) is especially represented in the anterior half of the upper third of the 
ascending parietal gyrus in the centres marked 9 and 11. (See Table 3.) 
Circumduction was never seen. 
Elbow .—We need only draw especial attention to the remarkably exact manner in 
which representation of extension of the elbow is limited to the upper fifth of the area 
experimented on, while flexion is equally the function of the lower three-fifths ; and to 
the existence of a very important zone of cortex, where the phenomenon of confusion 
is represented, this forming a border-land between the regions of extension and 
flexion. The explanation of this zone of confusion is easy, since the representation of 
the elbow—the movements of which occur in only one plane—admits necessarily of 
closely limited localisation. (See Table 3 and fig. 3.) 
Wrist .—In tabulating the movements of this joint, it was obviously necessary to 
separate its two distinct functions, viz., pronation and supination, on the one hand, 
and flexion and extension on the other. We will first discuss the latter function, as 
by far the more important. On Table 3 it is seen how extremely constant is the 
movement of extension, and a moment’s consideration will show that it is of funda¬ 
mental importance, for it is clear that the delicate movements of the fingers could not 
possibly be performed with any degree of accuracy and force unless the wrist be 
previously fixed in moderate extension, and consideration of this fact also explains why 
the wrist is especially provided with powerful extensor muscles which act with con¬ 
siderable independence. (See fig. 4.) 
In returning to the first-mentioned movements of the wrist, viz., pronation and 
supination, we have only to add that, as might be expected, supination is most 
marked in the lower two-thirds of the area, since it is here that we have also flexion 
of the elbow, i.e., bicipital action. The converse equally holds, viz., that pronation is 
associated with extension of the elbow. This association is clearly the outcome of the 
two great classes of action in animal life, viz., that of defence and that of feeding. 
The former of these is a coarse violent movement, and is naturallv associated in the 
upper part of the region with the centres for the large trunk and leg muscles, while 
the latter, more delicate, is represented near to the centres for the face and mouth.* 
(See Table 2.) 
Digits .—The representation of the fingers must be considered apart from that of 
the thumb, the movements of which are the most highly specialized in the limb. 
* Similar ideas have been previously suggested by Dr. Lauder Brunton, F.R.S. See Brain,’ vol. 4, 
p. 431. 
