42 
PROFESSORS V. HORSLEY AND E. A. SCHAPER 
39. 
Lesion 1. — Partial removal of the left gyrus fornicatus. A sharp scoop was carried 
along the convolution with the intention of removing the grey matter as completely 
as possible ; but the post-mortem examination of the brain showed that, as is so often 
the case in these cerebral ablations, the amount removed was far less than was 
anticipated. At two places only was there much destructive lesion of the convolution, 
viz., in front near the anterior extremity of the corpus callosum, and behind near the 
quadrate lobule. The remainder of the gyrus between these points is almost intact, 
except along its upper margin, near the calloso-marginal sulcus. The instrument must 
have been carried along the line of this sulcus, for the lower border of the gyrus 
marginalis is destroyed to a corresponding extent. 
Result. — The next day the animal does not react to tactile impressions applied to 
the right side of the trunk as far down as the flank, and also all over the right arm, 
and hardly reacts to a prick or jet of water on those parts, but the head and the hind- 
limb of the right side seem fairly sensitive. There is some muscular paresis of the 
whole right side. 
The loss of sensibility upon the right side was maintained, but in a gradually 
lessening degree, during seven weeks, when a further operation was performed, viz. : — 
Lesion 2. — Removal of the posterior part of the limbic lobe as it bends round the 
splenium of the corpus callosum. 
Result. — " It is doubtful if there is any difference produced by this second lesion. It 
is still the right arm and right side of the trunk which show diminished sensibility." 
Lesion 3. — Two weeks after the second operation the skull was removed over the 
left occipital region, the occipital lobe raised, and the posterior part of the hippo- 
campal convolution scooped away from behind. 
Result. — Our impression is that the anaesthetic condition of the right side of the 
body was better marked as the result of this third ablation, although we cannot 
positively affirm this. We will content ourselves with giving the results of a careful 
mapping out of the ansesthetic region which was made a fortnight after the third 
operation. So far as we could determine, the symptoms then recorded persisted 
without perceptible change until the animal was killed three months later. The 
testing was performed mainly by gentle and repeated prickings with a small pin, but 
the difference upon the two sides was also tested by induction shocks. 
"On the right side of the head, neck, and trunk no reaction is obtained until the 
flank is reached, when there is immediate manifestation of sensibility. The right 
leg reacts at once to a prick, but not to gentle scratching with the pin point, sufficient 
to produce marked reaction upon the left side. Of the right arm the elbow and palm 
of the hand react readily, the back of the fore-arm hardly at all, the back of the 
upper arm only slightly. Reaction is also obtained by stimulating in the axillary and 
pectoral regions. 
" There is distinct muscular paresis of both right limbs, but more of the arm than 
of the leg. 
