44 
PROFESSORS V. HORSLEY AND E. A. SCHAPRR 
destruction of the gyrus fornicatus upon the same side as the hippocampid lesion, 
but the post-mortem examination showed that the destruction of that convolution 
was not complete. Only about the middle third of the gyrus fornicatus was 
involved in the lesion, and even here at places the part next the corpus callosam 
remained undestroyed. On the other hand, an equal extent of the marginal gyrus 
along the calloso-marginal sulcus was injured. 
Result. — This second lesion again produced a very considerable deficiency of reaction 
to tactile impressions and a certain amount of deficiency of reaction to painful im- 
pressions over the whole of the left side of the body. There was also some paresis 
of the left leg. This condition persisted until the death of the animal ten days after 
the second operation. 
The lesions are shown in figs. 41a to D. 
42.* 
Lesion 1. — Kemoval of the anterior two-thirds of the left gyrus fornicatus. 
Result. — The immediate result was the production of a great diminution of sensibility 
over the whole of the right side of the body. The insensibility was for the first two 
or three days complete, even to pricking and a hot wire, on the right side of the 
trunk and in the right upper limb. A slight reaction is obtained on pricking the root 
of the tail on the right side, and more on applying the same stimulus to the right leg. 
There was also at first some muscular paresis on the right side, especially of the leg. 
A week after the operation the condition was much improved. 
There is now reaction over the whole of the right side to painful impressions, but 
often want of localisation of the seat of these impressions, a totally different part 
being scratched from that which is stimulated.t The muscular paresis is now scarcely, 
if at all, apparent. 
Recovery proceeded gradually, so that after a time tlie difference of sensibility of 
the two sides is hardly perceptible, except about the arm and shoulder and in the foot. 
Lesion 2. — Eleven weeks after the first operation, this last condition being 
still maintained, the right gyrus fornicatus was exposed, and injured by scratching its 
surface with a needle. This, however, produced no perceptible result, and after 
a fortnight the animal was killed and the brain examined, when it appeared that the 
permanent injury caused by the needle operation was so slight as to be almost 
imperceptible. 
The lesion of the left hemisphere is shown in fig. 42, Plate 7. 
43. 
Lesion. — The posterior part of the left hippocampal gyrus was destroyed from 
behind by raising the occipital lobe. 
* Exliibited to the Physiological Society, 
t Compare Nos. 36 and 37. 
