224 CEREBRAL LOCALIZATION 



astereognosis, inaccuracy of location, and slight 

 duUing of sensation over the ulnar border of the 

 hand. If the lesion had involved the postcentral 

 convolution, the sensory symptoms, in his experience, 

 would have been much more marked. The athetosis 

 was cured. 



Interference with sensation is of course no proof 

 that a cerebral tumour is in the cortex ; it may be 

 found with a lesion of the optic thalamus, internal 

 capsule, isthmus, pons, or medulla. In twenty-six 

 cases of hemiplegia due to some trouble in the internal 

 capsule, Bergmark found evidence of sensory im- 

 pairment in all who were intelligent enough to be 

 tested with accuracy by modern methods, although 

 there was never complete hemiansesthesia to all forms 

 of stimuli. 



The relations of the cerebral cortex, optic thalamus, 

 and mid-brain to various forms of sensation have 

 recently been made the subject of an interesting 

 research by Head and Gordon Holmes. The special 

 character of interference with sensation in lesions of 

 the cortex in the Rolandic area is the untrustworthi- 

 ness of the response. The stimulus will be felt at one 

 time but not at another ; the sensation may persist 

 after the stimulus is withdrawn, hallucinations may 

 be present, and local fatigue, affecting sensation in 

 the paralysed limb but not in the other, is easily 

 induced. All forms of sensation, heat, cold, tactile, 

 localization, stereognosis, and weight sense, may be 

 diminished, muscular sense (sense of passive move- 

 ments and of posture) being particularly liable to 

 reduction. 



