LESION OF DIFFERENT REGIONS OF THE CEREBRAL HEMISPHERES. 541 
though the lesions were somewhat complex, and, owing to the condition of the brain, 
not very easy of exact estimation. 
The temporary hemiopia to the left side is readily explicable by the lesions of the 
cortex and medullary fibres of the occipito-angular region. The very evident impair¬ 
ment of tactile sensibility of the left side—sensibility to mere contact being apparently 
completely abolished during the first two or three days, and deficiency being still 
observable for a whole fortnight after the operation—would seem to be in direct 
relation to the injury of the hippocampus and its medullary fibres, as this was the 
only lesion beside that of the medullary fibres of the posterior lobe. 
The more extensive destruction of the hippocampal region in the left hemisphere 
was associated with a more prolonged impairment of tactile sensibility on the right 
side, though from the first this was not abolished. There was also temporary impair¬ 
ment or abolition of hearing on the right, a fact which receives its explanation in the 
injury inflicted on the medullary fibres of the superior temporo-sphenoidal convolution. 
The lesion of the occipito-angular region reinduced for a time the impaired vision 
towards the left which had resulted from the lesion in the right hemisphere, but which 
had been recovered from ; but the persistent right hemiopia was evidently due, as had 
been diagnosed during life, to the lesion of the left optic tract. 
In consequence of this lesion there was atrophy of the brachium and anterior 
tubercle of the corpora quadrigemina on the left side, and atrophy of the right optic 
nerve. This showed itself during life in well-marked atrophy of the outer sector of 
both optic discs. 
The lesion in the left hemisphere implicated a portion of the basal aspect of the 
lenticular nucleus, but beyond the slight awkwardness of the movements of the left 
limbs, which might have been due to their defective sensibility, there was no other 
motor defect. 
Experiment 26 (Plate 30, figs. 117-124). 
In this animal the left hemisphere was exposed over the region where the middle 
temporo-sphenoidal convolution becomes continuous with the occipital lobe, the object 
being to obtain a better guide for directing the cautery along the hippocampal region. 
The wire cautery was passed through the convexity of the occipital lobe, above the 
annectent gyrus, downwards and forwards, with a view to break up the hippocampal 
region. (As to the actual course, see the post-mortem examination.) 
The animal, when let loose after the dressing of the wound, began to sprawl about 
almost immediately, and within a few minutes had climbed up on its usual perch. The 
limbs were all moved freely, but frequently the right foot slipped or was planted 
awkwardly. Tested with a heated wire, there was less marked sign of feeling on the 
right side than on the left, but sensation was evidently not abolished. 
An hour after the operation the animal was very active, running about its cage 
without any sign of weakness of the limbs. Vision seemed impaired towards the right, 
