224 Effects of Lesions of the Cerebral Hemispheres. [Jan. 24, 



Lesions of the frontal lobes are followed by descending degeneration 

 of the mesially situated tracts of the foot of the crus cerebri and cor- 

 responding fibres of the internal capsule, as seen in transverse sections. 

 The ultimate destination of these tracts is uncertain. They cannot 

 be traced in the anterior pyramids. 



Lesions entirely destroying the hippocampal region (the hippo- 

 campus major and gyrus hippocampi) and neighbouring inferior 

 temporosphenoidal region (without implication of the crus cerebri, 

 basal ganglia, or internal capsule) cause complete anaesthesia — cuta- 

 neous, mucous, muscular — of the opposite side of the body, without 

 motor paralysis. 



The degree of impairment of tactile sensibility in those cases 

 where it is not entirely abolished, is in proportion to the amount of 

 destruction of the hippocampal region. 



Lesions of the cornu ammonis alone, or gyrus hippocampi alone, 

 do not cause permanent impairment of tactile sensibility. The 

 duration of the effects of total destruction of the hippocampal 

 region has not been determined. 



No impairment of tactile sensibility has been observed in con- 

 nexion with any of the other cerebral lesions described. 



