LESION OF DIFFERENT REGIONS OF THE CEREBRAL HEMISPHERES. 535 
hippocampal and lower temporo-sphenoidal region from the rest of the hemisphere 
without injury to the crus cerebri or other structures. 
Many of the experiments were unsuccessful owing to miscalculation of the direction 
and depth of the lesions and consequent injury of the basal ganglia or crus cerebri. 
These it is not considered necessary to report, as any lesion of this kind was regarded 
as vitiating the whole experiment. 
In the others, all of which are reported, varying success was met with as regards 
the degree and limitation of the lesion to the hippocampal region. Unfortunately 
the mortality has been such as to interfere with the solution of some points of 
importance in connexion with the permanency of the effects of total destruction of 
the hippocampal region and its secondary results. 
Experiment 24* (Plate 29, figs. 103--109). 
The subject of this experiment was the same animal as that of Experiment 17. 
About two months and a half after the lesion of the motor region of the right side, 
the extremity of the left occipital lobe was exposed, and a director passed between 
the under surface of this lobe and the tentorium cerebelli approximately in the 
direction of the gyrus hippocampi. A wire cautery was then passed along the groove 
of the director with the view of destroying the cortex without going through the 
medullary fibres of the occipital lobe and hippocampal region. 
The animal, it wdl be remembered, was at this time partially hemiplegic on the left 
side. 
After the operation, when consciousness had returned, the conjunctival reflex was 
distinct on the left, but barely perceptible on the right. Thermal stimulation caused 
active withdrawal of the left foot, but no movement of the right. 
Two hours after the operation the animal was active and vigorous, with the motor 
powers of the right side unimpaired. 
The cremasteric and cutaneous plantar reflexes were distinct on the right side, but 
not perceptible on the left—the hemiplegic side. 
Sensibility was not abolished on the right, but much impaired as compared with the 
left. Severe thermal stimulation caused reaction on the right, but less marked than 
on the left. Pinching, pricking, &c., of the left limbs invariably caused signs of 
uneasiness and struggles to escape, whereas the same on the right caused no 
sign at all, or only very slight on increasing and prolonging the stimulation. The 
reaction to the vapour of acetic acid appeared less active in the right nostril than the 
left. Sight, hearing, and taste seemed quite as acute on the right as left. 
Next day the repetition of the tests of tactile sensibility revealed similar signs of 
impairment on the right; and again on the fifth day. The cutaneous plantar reflex of 
the right side was better than on the left, yet the right foot might be pinched 
or pricked without causing such vigorous reaction or signs of sensation as on the 
left. 
