THE NERVOUS SYSTEM 353 



speech-centres, quite distinct one from the other. Near the 

 visual area is the centre for seeing words, or rather the centre 

 for seeing the meaning of words. If this centre be diseased, a 

 written word is merely a crooked line. Behind the auditory 

 area is the centre for recognizing the meaning of words heard. 

 If it is interfered with, the most endearing or commanding 

 phrases produce no more impression on the hearer than a 

 bird's song. In front of the hand-area its localization is 

 less certain than that of the other three is the centre for 

 writing. In it are associated words heard or seen, with the 

 movements necessary for the making of letters. In the centre 

 first referred to, as being the one most often thrown out of 

 gear, which lies in front of the area for the mouth and throat, 

 words heard or seen are translated into movements of the 

 parts which give them sound. No other actions illustrate so 

 clearly the " law of neural habit." In the infant's brain 

 sounds of words are distinguished from other sounds. They 

 are associated with the objects which they name. Movements 

 of the mouth and throat, made at first ineffectively, blunder- 

 ingly, succeed after a time in securing the thing of which 

 they sound the name to the child's satisfaction. Thus, two 

 centres are gradually established in his mind. Sounds and 

 ideas of things are associated in the one ; words and ideas of 

 the movements necessary to their pronunciation in the other. 

 Either of the four speech-centres may be placed out of action 

 without the others suffering. A man may be able to write 

 without being able to read what he has written. He may read 

 aloud, although apparently deaf to speech. He may be unable 

 to write or unable to speak, although understanding what he 

 reads or hears. Aphasia, when partial, illustrates still further 

 the law of neural habit. The ability to remember nouns, 

 especially proper names, is most easily lost. Few are the people 

 who, as age advances, do not suffer from this failing. Even 

 the names which are most familiar elude the memory. From 

 one point of view this is strange. Nouns-substantive are the 

 words first learned. Of all words they have the most definite 

 objective association. But it is just their definiteness which 

 makes them difficult of approach when the apparatus of mind 

 is working badly. There are so few paths by which they can 

 be reached. Their mental associations are limited. A patient 



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