LESION OF DIFFERENT REGIONS OF THE CEREBRAL HEMISPHERES. 545 
on the right side the extremity of the cornu ammonis and nucleus amygdalae are seen 
intact. The central ganglia, crura, and optic tracts are free from lesion throughout. 
Remarks .—The lesion of the left hemisphere in this case, apart from that of the 
occipito-angular region, divided a portion of the medullary fibres of the gyrus hippo¬ 
campi and cornu ammonis, but the greater portion of these structures was uninjured. 
Slight and transient impairment of tactile sensibility only resulted. The impairment 
of vision towards the right would be accounted for by the lesion of the occipito-angular 
region ; so that the transient impairment of tactile sensibility would be in relation with 
the injury to the medullary fibres of the hippocampal region, as this was the only other 
portion of the brain which was the seat of lesion. There was no defect as regards 
hearing; and there was no lesion of the superior temp or o-sphenoidal convolution. 
On the right side, apart from the lesion of the occipital lobe, the destruction was 
limited in a most remarkable manner to the gyrus hippocampi, the whole of which, 
with the exception of the anterior extremity and portion immediately adjoining the 
collateral fissure, had been removed. The hippocampus itself, and the greater portion 
at least of its medullary fibres, had escaped injury. With this lesion of the gyrus 
hippocampi was associated, in evident causal relationship, a very marked impairment 
of tactile sensibility in all its forms. This, however, gradually diminished until at 
the end of ten days it ceased to be discoverable. 
Hearing was not in the slightest degree impaired by this bilateral cerebral lesion. 
The condition as to vision was rather a difficult one to determine as regards each 
eye. But it was clearly not dependent on any lesion of the optic tracts or nerves. 
All that could be made out was that vision was not permanently abolished towards 
the right side, but whether the hemiopia was symmetrical or not was not determined. 
The atrophy of the right optic nerve was purely secondary to the destruction of the 
visual centres of che cortex, and was not due to any direct injury of the optic tract or 
its connexions with the corpora quadrigemina or corpora geniculata. 
The fact that the right optic nerve was specially atrophied showed that the cerebral 
centres in relation with the right eye had specially suffered; but an exact estimation 
of the amount of lesion in the cortex and medullary fibres of the occipito-angular 
region in each hemisphere could not be made. 
Experiment 27 (Plate 31, figs. 125-132). 
In this case the left hemisphere was exposed in the region of the incisura prse-occi¬ 
pitalis and pli de passage from the middle temporo-sphenoidal convolution to the occipital 
lobe. With the aid of a director passed between the under surface of this region and 
the tentorium cerebelli, the third occipital convolution was divided by a horizontal 
incision, and another incision continuous with this was carried along posterior to the 
middle temporo-sphenoidal convolution. The portion of brain included between these 
two incisions, viz. : the inferior occipital, the lower temporo-sphenoidal convolution, and 
MDCCCLXXXIV. 4 A 
