ox THE FUNCTIONS OF THR CEREBRAL CORTEX. 
21 
about three-quarters of an inch, and the adjoining portion of the uncinate convolution. 
Such removal, although effecting an extensive lesion in this region, produced, however, 
no effect, so far as we could determine, upon the sensibility of the opposite side of the 
body, such as we had been led to expect from the experiments of Ferrier would 
have been the case. On communicating this result to Professor Ferrier, he suggested 
that the difference probably arose from the smaller extent of the lesion, especially 
of the uncinate gyrus, as compared with the cases published by him ; and we 
accordingly in further experiments endeavoured to effect a more complete removal 
of that convolution as well as of the hippocampus itself The result of this was that 
in many cases there was produced, as Ferrier has described, a unilateral diminution 
of sensibility affecting the whole of the opposite side of the body. This condition of 
hemianeesthesia, although fairly well marked, was in our experiments never complete, 
nor was it permanent ; and, indeed, in most instances it was found to have disappeared 
within a week of the operation. Since even with a tolerably extensive lesion in this 
region we were not always able to substantiate the fact that there was a diminution 
of sensibility produced, at least on testing the animals some hours after the operation, 
and since also, when a distinct effect was obtained, it was comparatively transient, it 
was difficult to be certain that the result yielded by the operation was really due to 
the removal of a part of the cortex connected with the consciousness of sensations, 
and might not be otherwise explained, as we have previously pointed out, by a 
disturbance of the function of other parts, which must always be produced by any 
extensive cerebral lesion ; and this explanation seems at all events as reasonable as one 
which assumes that it is exclusively the region in question which is concerned with 
the appreciation of tactile and painful sensibility. Another explanation is, however, 
possible, and would equally well fit in with the facts which we have to record. For, 
as we shall immediately show, the gyrus fornicatus is certainly connected with the 
sensibility of the opposite side of the body. Now the gyrus fornicatus is anatomically 
to be regarded as a direct continuation of the gyrus hippocampi (the two constituting 
the great limbic lobe of Broca).* It is probable, therefore, that the functions of the 
two are similar, and possible that, as in the case of the visual sensory area, after 
removal of a part, the remainder of the area can carry on, more or less efficiently, the 
functions of the whole. But, before discussing this possibility further, we will 
describe the results we have obtained from lesions of the gyrus fornicatus. 
Experiments upon the gy rus fornicatus. — We have endeavoured to remove the cortex 
of the gyrus fornicatus by exposing freely the upper surface of the hemisphere, 
drawing the brain gently away from the falx with retractors, and bringing to view 
the convolution in question, which could thus, with some difficulty it must be 
admitted, be got at and cut away to a greater or less extent by the aid of a specially 
constructed curved knive. We have operated in this way upon the gyrus fornicatus 
* In tlie Kangaroo, as Beevok Las shown, tlie microscopic structure is identical in both the gyrus 
fornicatus and gyrus hippocampi. 
