622 NERVOUS SYSTEM. 



of Reil ; and it is a curious fact that this part is found only in man and 

 monkeys, being in the latter very slightly developed. 



While the cerebral lesion in aphasia involves the left frontal lobe in the 

 great majority of cases, there are instances in which the right lobe alone is 

 affected, and these occur in left-handed persons. Aside from the anatomi- 

 cal arrangement of the arteries, which seem to furnish a greater quantity of 

 blood to the left hemisphere, it is evident that as far as voluntary move- 

 ments are concerned, the right hand, foot, eye etc., are used in preference 

 to the left, and that the motor operations of the left hemisphere are superior 

 in activity to those of the right. Bateman has quoted two cases of aphasia 

 dependent upon lesion of the right side of the brain, and consequent left 

 hemiplegia, in which the persons were left-handed ; and these, few as they 

 are, are important, as showing that a person may use the right side of the 

 brain in speech, as in the other motor acts. Although most anatomists have 

 failed to find any considerable difference in the weight of the two cerebral 

 hemispheres, Boyd has shown by an " examination of nearly two hundred 

 cases at St. Marylebone, in which the hemispheres were weighed separately, 

 that almost invariably the weight of the left exceeded that of the right by 

 at least the eighth of an ounce (4'5 grammes)." 



Broadbent has reported an examination of the encephalon of a deaf and 

 dumb woman. In this case the brain was found to be of about the usu 

 weight, but the left third frontal convolution was of " comparatively 

 size and simple character." 



Taking into consideration all of the pathological facts bearing upon the 

 question, it seems certain that in the great majority of persons, the organ 01 

 part presiding over the faculty of language is situated on the left side, at 01 

 near the third frontal convolution and the island of Reil, mainly in the 

 supplied by the middle cerebral artery. In some few instances the 

 seems to be in the corresponding part upon the right side. It is possible 

 that originally both sides preside over speech, arid the superiority of the lef 

 side of the brain over the right and its more constant use by preference ii 

 right-handed persons may lead to a gradual abolition of the action of the 

 right side of the brain, in connection with speech, simply from disuse. Thi 

 view, however, is purely hypothetical. In some cases of aphasia from lesior 

 of the speech-centre in the left hemisphere, recovery takes place, and occ 

 sionally " speech has been again lost when a fresh lesion occurred in thi 

 part of the right hemisphere " (Gowers). In the ataxic form of aphasia, the 

 idea and memory of words remain, and there is loss of speech simply fror 

 inability to co-ordinate the muscles concerned in articulate language. Pa 

 tients affected in this Avay can not speak but can write with ease and correct 

 ness. In the amnesic form of the disease, the idea and memory of language 

 are lost ; patients can not speak, and are affected with agraphia, or inability 

 to write. The motor tracts from the centre for speech pass to the anterior 

 portion of the posterior division of the internal capsule and thence throng! 

 the left crus, into the pons Varolii, where they decussate and go to the right 

 side of the medulla oblongata. 



