ON THE FUNCTIONS OF THE CEREBRAL CORTEX. 
13 
the paralysis of the lower limb is not sufficiently marked to prevent the animal from 
using it in the ordinary movements of walking and climbing, although there is distinct 
and permanent lameness in progression. 
We have not performed this ablation bilaterally, nor have we made more than one 
or two experiments upon the effect of ablations of localised portions of the external 
surface. Such as we have done, however, afford strong confirmation of the results 
obtained by electrical excitation. Thus we have found that removal of that part of 
the ascending parietal gyrus, excitation of which causes movements of the wrist and 
fingers, is followed by permanent paresis of those parts, the function of no other part 
of the body being interfered with. And the removal of the arm-area produces 
paralysis of the opposite arm without any accompanying paresis of face, head, trunk, 
or leg. Nor does there appear to be any real recovery from the paralysis which may 
have been produced by the lesion, althougli in all lesions of the motor areas, when 
any portion of an area is left, it may happen that the muscles which are governed 
from that portion may by practice succeed in imperfectly reproducing some of the 
movements which are ordinarily produced by the paralysed muscles. The effects of 
ablation of the motor cortex upon sensibility will be referred to later on. 
Results of ablation of the marginal gyrus. — The results of bilateral ablation of the 
marginal gyrus from the level of the anterior extremity of the corjDus callosum to the 
posterior termination of the convolution just behind the level of the upper end of the 
furrow of Rolando is, considering the relatively small extent of the cerebral cortex 
thus destroyed, most remarkable. The operation is followed by complete paralysis of 
the trunk-muscles, some paresis of the arms, and very extensive paralysis of the 
muscles of the legs. The paresis of the arms chiefly affects some of the shoulder- 
muscles, especially those which retract and at the same time elevate the scapula ; it is 
less marked in the case of the muscles of the upper arm and fore-arm, and hardly, if at 
all, perceptible in those moving the fingers. The paralysis of the leg extends to almost 
all the muscles, both those which are intrinsic and those which connect the limb with 
the trunk, with the exception of certain flexors of the hip — probably the iliopsoas 
and the tensor vaginae femoris. The attitude and general appearance of a Monkey in 
which this double lesion has been produced are very striking (fig. 20, Plate 3). 
Instead of sitting up with back somewhat curved, in the manner normal to Monkeys, 
an animal which has been submitted to this operation lies prone, with legs and 
feet outstretched (or at most with flexed hips), back flat, tail straight and motionless, 
and arms put forward to clutch at any neighbouring object. The head retains its 
power of rotation as well as flexion and extension, and the movements of the eyes 
and facial muscles appear normal. The animal frequently props itself upon its elbows, 
but never assumes the normal sitting attitude. If the Monkey desires to sit up, it can 
only do so by dragging itself into the sitting posture by its arms* and hands, and 
holding on by these to the wires of the cage or to any neighbouring object. If the 
hold be detached, the animal immediately tends to fall over. Progression is effected 
