CEREBRAL LOCALIZATION 165 



mais je ne parviens pas a le faire " : this' just expresses 

 the condition. 



In some of the cases, there is imperfect recognition 

 of objects or of their uses (agnosia), but these are 

 complicated and cannot be described here. 



It is an important fact that apraxia of the left 

 arm is common in right hemiplegics, whereas apraxia 

 of the right arm rarely occurs in left hemiplegics ; 

 moreover, in the cases where there are apraxia of the 

 left side and hemiplegia of the right, there is evidence 

 that the lesion is cortical, not in the internal capsule. 

 Thus Liepmann examined eighty-three hemiplegic 

 patients, with these results : 



Forty-two had left hemiplegia ; they could nearly 

 all obey directions with the right arm. 



Forty-one had right hemiplegia ; of these 20 had 

 apraxia of the left arm, and 14 in this group also 

 had aphasia ; 21 had no apraxia, and of these only 

 4 had aphasia (in most of the other 17 cases, the 

 lesion was probably in the internal capsule). 



Of course, as left-handed persons form one-twentieth 

 of the community, it is possible to find a few cases of 

 left hemiplegia with right apraxia. 



There is good ground, then, for believing that the 

 centres which consciously initiate voluntary move- 

 ments for both sides of the body are limited to the 

 left cortex in right-handed people, and that the pre- 

 central convolutions are merely the departure 

 platforms for messages from the brain to the cord. 

 Instructions are sent to the right precentral convolu- 

 tion by way of the corpus callosum. It is still in 

 doubt whether the above-mentioned initiating centre 



