LESION OF DIFFERENT REGIONS OF THE CEREBRAL HEMISPHERES. 559 
Tn the region of the middle of the collateral fissure, the transverse incision, before 
described (cut obliquely), extended so far inwards as partially to sever the medullary 
fibres of the hippocampal region (figs. 170, 171), the cornu itself and the cortex of the 
gyrus hippocampi being free from lesion. Towards the extremity of the descending 
cornu the breaking up and detachment of the gyrus hippocampi and cornu ammonis 
was more complete, the whole of the anterior extremity of the temporo-sphenoidal 
lobe being more or less broken up (fig. 172). 
The central ganglia, internal capsule, optic tracts, and crura were altogether intact. 
Remarks .—This case is in some respects very extraordinary, and particularly with 
reference to the lesion of the left hemisphere. It would seem practically impossible 
to limit an experimental lesion so precisely to the fascia dentata and alveus of the 
cornu ammonis, as occurred in this case, without causing injury to other structures— 
the optic tract or crus cerebri. But no such injury was present. The case is also 
altogether unique in the symptoms which were induced. Instead of temporary 
annihilation, or impairment of tactile sensibility, there was for a time well-marked 
exaltation of sensibility on the opposite side of the body. The lesion, therefore, instead 
of destroying the centres of tactile sensation, seems to have thrown them into a state 
of hyperactivity. It may he supposed that the slight destructive lesion of the 
hippocampal region was accompanied by active congestion of the uninjured portions. 
In the right hemisphere the lesion of the hippocampal region was only partial, being 
confined to the anterior half, and consisting mainly in division of the medullary fibres 
passing to the gyrus hippocampi and cornu ammonis. The anterior half of the middle 
and inferior temporo-sphenoidal convolutions were, however, much broken up and 
disorganised. 
The affection of tactile sensibility, at first well marked, ceased to be perceptible 
after a few days, and apparent complete recovery took place. 
With the exception of slight impairment of vision to the right side of a temporary 
character, due to the lesion of the left occipital region, no other sensory or motor 
defect, beyond the affections of tactile sensibility above described, appeared to result 
from the bilateral lesion in this case. 
Experiment 33 (Plate 36, figs. 173-181). 
In this case the extremity of the left occipital lobe was exposed, and a director 
passed between the under surface and the tentorium cerebelli downwards and forwards 
in the direction of the gyrus hippocampi. A wire cautery was pushed along the 
groove, and afterwards a porte caustique tipped with nitrate of silver. 
Within an hour after the operation the animal was able to get up and move about, 
but the limbs of the right side were used awkwardly and planted abnormally. 
At this time, though severe thermal stimulation caused some sign of sensation on 
the right side, the reaction was much less marked than on the left, and a degree of 
