LANGUAGE FACULTIES 663 



The language faculties make a distinct advance when the child learns to 

 read and write. The symbols of spoken words used in written language 

 words and the letters of which they are composed are inculcated in the same 

 way as spoken words, and at the same time the ability is acquired to reproduce 

 these symbols in writing. The movements used in writing, just like other move- 

 ments, are controlled by various afferent impulses. 



Our powers of language are made up therefore of the following compo- 

 nents : ( 1 ) Memory pictures of the written and spoken words ; ( 2 ) the ability 

 to make the coordinated movements necessary in speech and writing; (3) 

 constant control of this ability through various afferent pathways. 



Lesions in certain regions of the cortex or in the corona radiata produce 

 disturbances of greater or less extent in these delicate mechanisms, which are 

 comprehended under the name of aphasia,, and differ in kind and extent 

 according to the place of lesion. 



One of the simplest forms of aphasia is that of alexia, or word blindness, 

 which is characterized by the inability to recognize written or printed letters 

 or to compose words of them. This disorder (in right-handed people) follows 

 injury to the white matter of the left angular gyrus and of the second occipital 

 convolution, the corresponding cortex remaining uninjured. Simple alexia 

 would thus be produced by interruption of the association fibers connecting 

 the visual cortical area with other cortical regions which are active in the 

 use of language. When the cortex alone of the angular gyrus is affected, 

 alexia does not ensue, and this may be taken as a proof that that portion of the 

 cortex is not, as has been supposed by many authors, the " center " for reading. 



Alexia may occur without affecting the ability to speak, and this is readily 

 understood when we remember that aside from writing reading is the latest 

 acquirement in the development of the language powers, and might well exer- 

 cise but a slight influence on the speech mechanism pure and simple. 



It is possible for the patient to be able to write even when he cannot read, 

 and this is explained by supposing that the association pathways which are 

 active in writing have escaped the lesion. Such a patient may even succeed 

 in deciphering script or printing by executing the appropriate movements for 

 making the letters which he sees, but would not otherwise comprehend. In 

 this case he reads by using the memory pictures of these movements and by 

 bringing them through association fibers into connection with the cortical areas 

 which mediate the necessary movements of the organ of speech. 



Other disorders of the language powers are produced by lesions within the 

 red area in Fig. 296, and the white matter lying immediately under it. In 

 right-handed people it is always the left hemisphere which is affected. These 

 disorders differ both in kind and extent, and can be divided into two groups 

 motor and sensory aphasia according as the expressive or the perceptive 

 phase of language is the more affected. Between the two are various inter- 

 mediate modifications. 



Motor aphasia, which through the work of Broca has been of so much 



importance for the development of our views concerning the functions of the 



cerebrum (see page 631), appears in its purest and simplest form when only 



the special motor functions of speech are arrested. In this case the person 



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