LESION OP DIFFERENT REGIONS OF THE CEREBRAL HEMISPHERES. 539 
reveal any marked abnormality of the discs, but examination six months after the 
operation discovered signs of atrophy of the outer side of the right disc, which was 
the only one examined at this time. 
My colleague, Professor McHardy, reported, on examination of the discs nine months 
after the operation, and on comparison with those of a normal Monkey, that there was 
well marked atrophy and pallor of the outer side of both discs. 
The right hemiopia continued till the animal’s death by chloroform eighteen 
months after the first operation. 
Post-mortem examination .—The dura mater was adherent over each occipital lobe, 
at a point corresponding to the anterior extremity of the first occipital sulcus. The 
occipito-temporal region of both hemispheres was also more or less adherent to the 
dura mater of the middle fossa, more on the left than the right. 
When the hemispheres were removed it was found that the cranial nerves were 
intact, but the right optic nerve was only about half the size of the left—the difference 
being greatest in the vertical diameter. 
The optic tract on the right side was quite normal, and could be followed round the 
crus to the corpora geniculata freely without any sign of adhesion or injury. 
The left optic tract was appreciably thinner and flatter than the right, and on being 
followed round the crus it was found that the portion proceeding to the corpus 
geniculatum externum had been sheared off by the cautery. The portion passing to 
the corpus geniculatum internum was intact, as well as the brachium of the testis. 
But the anterior brachium and the anterior tubercle of the corpora quadrigemina 
were distinctly smaller than on the right side. There was no lesion of these parts, 
however. The cautery had, with the most remarkable precision, just grazed and 
divided the optic tract at its junction with the corpus geniculatum externum, leaving 
everything else uninjured. 
Right hemisphere .—At the anterior extremity of the first occipital sulcus on the 
convex aspect of the occipital lobe there was an erosion where the membrane was 
adherent; and in the centre of this an orifice, the point of entrance of the cautery. 
The course of this, not visible on the surface otherwise, was indicated by a small rent, 
a few millimetres in extent, situated at the lower extremity of the inferior or third 
temporo-sphenoidal convolution, external to the anterior extremity of the gyrus 
hippocampi The course, therefore, of the sinus corresponded almost exactly with the 
collateral fissure. 
The exit of the cautery is marked by a X on fig. 110. 
Left hemisphere .—On the convexity of the left occipital lobe above the anterior 
extremity of the first occipital sulcus there was an erosion similar to that on the 
right, trenching on the posterior limb of the angular gyrus. In the centre of the 
erosion was a deeper depression, indicating the entrance of the cautery. The direction 
of the cautery was next indicated externally by a groove in the gyrus hippocampi, 
internal to the collateral fissure. 
3 z 2 
