FUNCTIONS OF THE CEREBRAL HEMISPHERES 455 



said to him and has been stated to suffer from no impairment of his intelli-* 

 gence. 



(2) Sensory aphasia, or aphasia of Wernicke. This condition was con- 

 nected by Wernicke with the existence of lesions in a fairly wide area/known 

 as the area of Wernicke, which involves the supra marginal and angular gyri 

 and the hinder portions of the first and second temporo-sphenoidal convo- 

 lutions. In these cases -there may be limited power of speech, but there 

 is serious impairment of the intelligence and especially of the power of 

 appreciation of spoken w r ords, so that the patient does not understand what 

 is said to him. This condition may or may not be attended with alexia, loss 

 of power to read. Any impairment of the motor processes of speech which 

 is present is due rather to the inability of the patient to appreciate 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 unaltered. 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-psychic and auditory psychic 

 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 external capsule. The statement 



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



