208 



PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



to speak can be again acquired by education of new centers.* 

 Some recorded cases seem to indicate that this re-education is 

 possible in the young, while in the old it is more difficult or impos- 

 sible. We express our thoughts not only in spoken but also in 

 written symbols. As this latter form of expression involves a 

 different set of muscles and a different educational experience, 

 it is natural to assume that the complex associations concerned, or, 

 to use a convenient expression, the memory centers, should involve 

 a different part of the cortex. It is, in fact, observed that in some 

 aphasics the loss of the power of writing, a condition designated 

 as agraphia, is the characteristic defect, rather than the loss of the 

 ability to use articulate language. The area in which the motor 

 'associations for the act of writing are located has been placed 



in the middle or sec^ 

 ond frontal convolu- 

 tion contiguous to "the 

 cortical motor centers 

 for the muscles of the 

 arm 'and hand (W; 

 Fig. 91). 



Sensory ''Aphasia. 

 In sensory aphasia f 

 (amnesia) the individ- 

 ual suffers from an 

 inability to under- 

 stand spoken or writ- 

 ten language, and as 

 the cortical centers for 

 hearing and seeing are. 

 situated in distinct 

 parts of the brain, we 

 should expect that the 

 mechanism for the 



'association, in one case of visual memories of- verbal symbols with 

 certain concepts and in the other case of auditory memories, should 

 also be located in separate regions. Inability to understand spoken 

 language, or word-deafness, is, in fact, usually attributed -to a 

 lesion involving the- first temporal convolution- contiguous -to the 

 cortical sense of hearing (H, Fig. 91), while loss of power to under- 

 stand written or printed language, word-blindness, is traced to 

 lesions involving the inferior parietal convolution, the gyrus angu- 

 laris, contiguous to the occipital visual center (V ', Fig. 91). These 

 * See Mills, "Journal of the Amer. Med. Assoc.," 1904, xliii. 

 t Consult Starr, "Aphasia," "Transactions of the Congress of American 

 Physicians and Surgeons," vol. i, p. 329, 1888; also Monakow, "Gehirn- 

 pathologie, 1906. 



Fig. 91. Lateral view of a human hemisphere; 

 cortical area V, damage to which produces "mind- 

 blindness" (word-blindness); cortical area H, damage 

 to which produces "mind-deafness" (word-deafness); 

 cortical area S, damage to which causes the loss of- 

 audible speech ; cortical area W, damage to which abol- 

 ishes the power of writing. (Donaldson.) 



