FUNCTIONS OF THE CEREBRAL HEMISPHERES 513 



what he himself is saying, so that there is here a species of sensory 

 paralysis in the higher sphere of neural processes. 



(3) Anarthria. This is a condition in which there is marked 

 impairment of the motor powers of expression, although intelligence 

 and appreciation of speech, both spoken and written, may be un- 

 altered. This condition is generally associated with lesion of the 

 white matter of the external capsule as it passes round the lenticular 

 nucleus. 



There are, however, considerable difficulties in the acceptation of 

 this traditional classification. Microscopic examination of Broca's 

 convolution shows a type of cortex entirely different from that part, 

 viz. the psycho-motor area of the ascending frontal convolution, 

 which is concerned with the higher cerebral processes resulting in 

 movement. Its structure is in fact identical with that described 

 by Campbell as the ' intermediate precentral area ' and regarded 

 as characteristic of the association areas. Moreover it is difficult 

 to comprehend how a function such as speech, with its enormously 

 complex mechanism, could be limited to so small a portion of the 

 brain as Broca's convolution. The neural basis of language must in 

 fact be co-extensive with the sensory centres (the projection spheres) 

 and with the whole region of lower association. We might indeed 

 speak of auditory and visual word-centres as located in the visuo- 

 psychical and auditory psychical centres. There is probably, 

 however, no word, still less a collection of words, expressing an idea, 

 which does not involve the activity of practically all parts of the 

 cerebral cortex. As Bolton * points out, " a word, such as ' mouse,' 

 at once sets in effect processes of association which pass to every 

 projection sphere with the solitary exception of the gustatory, and 

 even this may be aroused in a person who has eaten a fried mouse in 

 the hope of thereby recovering from an attack of whooping-cough." 



A careful examination of an extensive series of cases by Marie 

 has shown, in fact, that Broca's aphasia does not exist as a result 

 of lesions of Broca's convolution. This part of the brain may be 

 destroyed without any disorder of speech. The cases described by 

 Broca of motor aphasia are really cases of sensory aphasia from 

 lesion of Wernicke's area, combined with anarthria due to subcortical 

 injury of the fibres of the internal capsule. The statement that there 

 is no loss of intelligence in these cases of so-called motor aphasia 

 does not bear investigation. Although as patients they may comport 

 themselves reasonably, as soon as they have to perform any duties 

 which have been learnt by them in connection with their ordinary 

 avocations they show their deficiency. They are incapable of 

 transacting ordinary business, at any rate to the extent to which 



' In his admirable article in Hill's " Further Advances in Physiology." 



33 



