APHASIA. 



775 



supplemental action of the corresponding region of the right hemi- 

 sphere, is proved by the fact that in some of these cases speech has been 

 again lost when a fresh lesion occurred in this part of the right 

 hemisphere. This supplemental action occurs in the sensory as well as in 

 the motor functions. It occurs far more readily in children than in 

 adults . . . Hence it is probable that speech processes go on more 

 J equally in the two hemispheres in childhood than they do in adult life. 

 It is also highly probable that there are individual differences in this 

 respect among adults." 1 Two processes are involved in speech as in 

 other forms of volitional expression, the one involving sensory, the 

 other motor regions of the cortex. Thus the idea of words may be 

 aroused through the senses of hearing, sight, or touch, and the parts of 

 the brain where these perceptions occur are connected with the speech 

 centre proper, which is an association centre, situated mainly if not 

 entirely in the posterior part of the third left frontal convolution. 2 

 Accordingly, we may have aphasia of certain kinds from inability to 

 express words heard or words seen, pro- 

 duced by lesions in the sensory areas 

 (" word - deafness," " word - blindness "). 

 This is spoken of as " sensory aphasia " 

 (Wernicke). Such forms of aphasia 

 occur from lesions of the temporal region 

 (especially the superior gyrus), and of 

 the occipital region respectively, or both 

 motor and sensory aphasia may be com- 

 bined. 



There may be inability to recollect 

 words, to revive the word images (verbal 

 amnesia). Patients with this affection 

 can repeat words after you when bid- 

 den, which is not possible in cases of 

 so-called motor aphasia. 



Further, lesions producing aphasia 

 or amnesia may occur in the fibres con- 

 necting the several centres 3 sensory 

 and motor ; this is illustrated by the 



appended diagram (from Gowers), in which S is the speech centre; 

 A the centre for movements of the hand ; SC fibres from the speech 

 centre to the corpus callosum and opposite hemisphere ; Sm, Am, fibres 

 to the internal capsule. A lesion at x must cause permanent aphasia, 

 since it involves both the fibres to the internal capsule and those to 

 the corpus callosum, but would not cause agraphia (inability to write 

 intelligibly), for impulses can still pass from S to A ; one at y might 

 cause only transient aphasia, the impulses from S being able to pass 

 through the corpus callosum to the opposite speech region. 



There is abundant evidence that amnesia and even complete aphasia 

 may be produced by lesions of the cortex of the left hemisphere else- 

 where than in Broca's convolution. Thus, as has already been stated, 4 



1 Gowers, "Lectures on the Diagnosis of Diseases of the Brain," London, 1885, p. 125. 

 See a case reported by T. Barlow, Brit. Med. Journ., London, 28th July 1877. 



2 Broca, " Sur la siege de la faculte de langage articule"," Bull. Soc. anat. de Paris, 

 1861 and 1863. 



3 De Watte ville, Progres mdd., Paris, Mars 1875. 



4 Page 763. Of. Hitzig, Arch. f. Psi/chiat., Berlin, 1884, Bd. xv. S. 274. 



FIG. 353. Diagram to show the 

 manner in which lesions of inter - 

 nuncial fibres may produce aph- 

 asia. Modified from Gowers. 



