ON THE FUNCTIONS OF THE CEREBRUM 331 



vision, and that the time-honoured localisation of the motor speech 

 centre in the cortex of the posterior portion of the third frontal 

 gyms (the speech area of Broca) is incorrect, are of so revolu- 

 tionary a nature that the reader may well require more evidence 

 of their truth than is afforded by the papers even of so renowned 

 a neurologist as Pierre Marie. Such evidence as can be derived 

 from the psycho-physiological study of the subject of language, 

 and from the results of recent research on cortical localisation and 

 cerebral function, the writer has endeavoured to produce. 



Before indicating the views of Marie, it is desirable to refer 

 shortly to the theory of aphasia, advanced almost simultaneously 

 by Monakow in 1906. This investigator throws doubt on the 

 accepted localisation of the speech centre, and expresses the 

 opinion that aphasic disorders are caused less by destruction of 

 certain special regions of the cerebrum than by local losses of 

 functional continuity between the various centres which together 

 constitute the language mechanism. To this disturbance of 

 functional continuity he applies the term diaschisis. He indicates 

 that local affection of a connecting tract of fibres may cause tem- 

 porary suspension of the functions of one part of the mechanism 

 by removing from this the stimulus to action which normally 

 proceeds from another part. On the other hand, relatively inde- 

 pendent parts of the mechanism may pass into a state of abnormal 

 activity from lack of the controlling impulses which normally 

 proceed to them from other portions. Disturbances of local 

 function may thus arise in consequence of lesions situated in 

 different parts of the brain. 



This theory is propounded by Monakow to explain the frequent 

 discrepancies which exist between the clinical symptomatology 

 and the anatomical lesions of cases of aphasia. 



He points out that many cases of aphasia occur in which search 

 for the expected lesion gives a negative result ; that a still larger 

 number of cases recover although the lesion persists and even 

 becomes more extensive ; and that aphasic disorders often persist 

 in cases in which the lesion is found to be situated beyond the 

 limits of the speech area. He further remarks that " sensory 

 aphasia " may occur with lesion of Broca's gyms, and " motor 

 aphasia " with lesion of the zone of Wernicke ; and that at times 

 the symptomatology varies greatly in cases in which the situation 

 and relations of the lesion are practically identical. 



