LANGUAGE AND BRAIN DISEASE. 779 



Destruction of the motor speech center causes a much more 

 extensive interference with the use of language. The motions of 

 the vocal organs being no longer co-ordinated, an inarticulate 

 jargon, or the senseless repetition of a word or phrase, is all that 

 is left of the power to talk. The ability to write is also lost. 

 Reading aloud is, of course, impossible ; but it is also a matter of 

 common observation in such cases that the ability to understand 

 print is lost or greatly impaired. This proves that in most per- 

 sons direct associations between visual words and ideas, if they 

 exist at all, are too weak to be depended upon. So the under- 

 standing of spoken words is the only way of using language that 

 is independent of the motor speech center. 



But it is destruction of the auditory center that causes the 

 most extensive loss of language. In such a case words (though 

 they may be heard through the right side of the brain) are not 

 understood. This failure to understand is called word-deafness. 

 But there are other serious defects. Although the vocal appa- 

 ratus is in perfect order, and there are ideas seeking expression, 

 the words uttered are mutilated, deformed, and often totally dif- 

 ferent from the ones intended, so that intelligible speech is well- 

 nigh impossible. This shows that in talking the most important 

 association impulses do not go directly from the centers for ideas 

 to the motor speech center, but to the auditory center, which, re- 

 membering the sounds, by fresh impulses arouses the motor center 

 to utter them. Writing is still more interfered with, because it 

 depends upon the utterance-memory, which goes astray without 

 the sound-memory. 



Does destruction of the auditory center also prevent reading ? 

 We should expect it to do so, from the way in which reading is 

 learned, and excellent authorities say that it does. There is not 

 enough simple and direct evidence (consisting of the inability to 

 read during life, followed by the discovery of disease limited to 

 the auditory center after death) to prove this, on account of the 

 small number of available cases and the lack of attention to read- 

 ing in the observation of many of them. Making allowance, how- 

 ever, for the difficulties in the way of gathering direct evidence 

 on this point, the cases published support the view that in most 

 persons the auditory center is essential to the understanding of 

 what is read. But there is other evidence that is quite convinc- 

 ing. We have seen that in reading the visual center can not, as a 

 rule, call up the ideas, else destruction of the motor speech center 

 could not interfere with reading as it does. Nor is the motor 

 speech center directly connected with the centers for ideas ; if it 

 were, destruction of the auditory center could not interfere with 

 talking as it does. This leaves only the auditory center, which is 

 abundantly capable, for the sounds of words readily awaken ideas 



