76G COKTICAL MOTOR REGION IN MAN [Book hi. 



we give at the same time diagrams Figs. 134, 135 illustrating 

 the nomenclature of the surface of the human brain. 



One area is of special and instructive interest. Speech is 

 an eminently ' skilled ' movement. We have seen that in the 

 monkey the area for the mouth and tongue lies at the ventral 

 end of the central fissure or fissure of Rolando, ventral to the 

 arm area, and that the extreme ventral and front part of the 

 motor region just above the fissure of Sylvius supplies an area 

 which we marked as that of phonation (Fig. 123). In the monkey 

 the area of phonation is determined by experimental stimulation ; 

 in man, in a similar position, on the third or lowest frontal con- 

 volution, sometimes called Broca's convolution, ventral to and in 

 front of, and probably overlapping backwards the area which in 

 Fig. 136 is marked 'face' and which includes the mouth and 

 tongue, clinical study has disclosed the existence of an area which 

 may be spoken of as the area of ' speech.' Lesions of the cortex 

 in this area cause a loss of or interference with speech, the con- 

 dition being known as aphasia ; to this we shall presently return. 

 In Fig. 136 this area is shewn in an approximate manner. 



The movements of speech are essentially bilateral movements. 

 In the dog and monkey various bilateral movements may be 

 excited by stimulation of the appropriate area in either hemi- 

 sphere ; and analogy would lead us to suppose that in man, the 

 movements of speech would be connected with the speech area 

 in both one and the other hemisphere. The results of lesions 

 however shew that it is in most cases especially the left hemi- 

 sphere which is connected with speech : it is a lesion in the third 

 frontal convolution of the left hemisphere, often associated with 

 other lesions of the same hemisphere leading to paralysis of the 

 right side of the body and face, which causes aphasia, it being 

 only in exceptional cases that the condition results from a lesion 

 of the corresponding area of cortex on the right hemisphere. 



In man, then, clinical study corroborates the conclusions 

 deduced from the experimental investigation of the dog and of 

 the monkey, but still leaves us in uncertainty as to the question 

 what, and what alone are the absolutely permanent effects of 

 the loss of a cortical area and of nothing else. On the one hand, 

 in the cases in which recovery of a movement follows upon its 

 loss or impairment, it is open for us to suppose that the lesion 

 itself was temporary, and that with the cure of the malady the 

 cortical area regained its normal condition. On the other hand, 

 where the disease continues, the permanency of the loss of any 

 movement may be attributed to the disease doing more than 

 merely suspend the function of the cortical area. Aphasia, 

 especially in young persons, has been followed by recovery, but 

 in such cases it has been supposed that the dormant area on the 

 right side has been awakened to activity by the loss of the left 

 area; and in support of this view cases have been recorded in 



