LESION OF DIFFERENT REGIONS OF THE CEREBRAL HEMISPHERES. 543 
evidently acute on both sides. Vision, however, was profoundly impaired on both 
sides, but no definite determination could be made as to the exact condition on each 
side. 
On the third day on the animal being tested as regards tactile sensibility there was 
still very perceptible impairment on the left side, though not so great as before. 
Vision was still defective, but it was not yet clear how much each eye was relatively 
affected. 
There was still less reaction to heat on the left side than on the right. Ammonia 
held before the nostrils respectively, caused more active reaction on the right side. 
On the ninth day the difference as to reaction to tactile stimulation on the two sides 
was barely perceptible. Vision was still defective, but during the next few days 
further tests showed that there was absolute hemiopia towards the left, while vision 
was retained towards the right. The animal readily seized food, &c., offered it on the 
right, but lost it towards the left. 
From this time onward no further change occurred, the animal remaining absolutely 
blind towards the left. It was killed with chloroform nearly three months after the 
first operation. 
Post-mortem examination. — On removal of the brain it was seen that on cutting the 
cranial nerves the right optic nerve was considerably smaller than the left. 
The under surface of the temporo-sphenoidal lobes was in points adherent to the 
dura mater in the middle fossae, corresponding to the lesions of the hemispheres about 
to be mentioned. 
There was no effusion, and the crura cerebri, pons, and other structures at the base 
were absolutely normal in appearance. 
On tracing the optic tracts, which was readily done, there being no adhesion of the 
pia mater to them, they could be cleanly followed to the corpora geniculata. On the 
right side, close to the lesion in the hemisphere, there was a yellowish look of the 
corpus geniculatum externum and extremity of the pulvinar ; but there was no soften¬ 
ing or solution of continuity, and the discoloration was removed with the pia mater, 
being of the nature of mere imbibition from the adjacent lesion of the hemisphere. 
The corpora quadrigemina and the anterior brachia were clearly distinct and normal in 
appearance. 
Left hemisphere .—On the convex aspect of the occipital lobe, at the anterior 
extremity of the first occipital sulcus, there was a deep incision running parallel to the 
parieto-occipital fissure and extending upwards almost to the longitudinal fissure; the 
upper extremity running into this fissure. It was seen that the occipital lobe was thus 
injured to a much greater extent than had been supposed in the first operation. This 
deep gash in the occipital lobe led downwards and forwards to a sinus which became 
visible as a round hole in the middle of collateral fissure. From this point a groove 
extended forwards, following the course of the collateral fissure to its anterior ext remit} 7 . 
The gyrus hippocampi was injured at the margin of the collateral fissure where the 
