ON THE FUNCTIONS OF THE CEREBRAL CORTEX. 
43 
" There is hemiopia ; objects on the right side of the mesial plane not being seen." 
This is accounted for by the fact that the interference with the occipital lobe which 
occurred in the two later operations produced, as the post-mortem examination 
showed, extensive softening of that portion of the brain. 
The superficial extent of the lesions is represented in fig. 39. 
40. 
Lesion. — A cut was made along the anterior two-thirds of the right gyrus 
fornicatus, and the grey matter of the convolution was completely scooped away. 
The post-mortem examination showed that the marginal gyrus was also slightly 
injured, especially in the prefrontal region, and there were some small patches of 
softening on the external surface which had probably been caused by the drawing 
aside of the brain in endeavouring the better to reach the gyrus fornicatus. 
Result. — There was at first some paresis of the limbs and of the facial muscles on 
the left side. For ten days or more no reaction whatever was obtained either by 
tactile or painful impressions (pricks) applied to the left side, although the reaction 
was marked on the right side. " Even a hot wire causes very slow reaction, and the 
impression is apparently not localised." After this time there was some return of 
sensibility so far as painful impressions were concerned, the improvement being most 
marked at the back of the fore-arm. 
A month after the operation "reaction to painful impressions is manifested over the 
whole of the left side, but much less markedly than on the right side ; but there is still no 
reaction to tactile impressions applied to the left side. After a time, however, tactile 
impressions begin to produce reaction upon the left side also, but they are responded 
to far less markedly than on the right side." This was still the case ten weeks after 
the operation, when a second lesion, viz., the removal of the left gyrus fornicatus, was 
attempted, but proved fatal. 
The lesion in the right hemisphere is shown superficially in fig. 40a, Plate 7, 
and in section in fig. 40b. 
41. 
Lesion 1. — Destruction of the middle and posterior part of the right hippocampal 
gyrus from behind by raising the occipital lobe. 
Result. — The immediate result produced by this operation was to cause almost 
complete loss of reaction to tactile impressions in the left limbs and on the left side 
of the trunk, and greatly diminished reaction to painful impressions. The left ear 
and the left side of the head and face did not participate in this condition, which 
persisted for a few days, becoming gradually less marked, so that ten days after the 
operation the difference of reaction upon the two sides of the body was only slight. 
Seven weeks after the establishment of the first lesion, by which time no difference 
of sensibility could any longer be detected upon the two sides, a second operation 
was performed upon the same animal. This consisted (Lesi'07i 2) in the attempted 
G 2 
