CH. LYII.] DEFECTS OF SPEECH 809 



due to meningeal haemorrhage affecting the grey cortex of the left hemisphere. 

 These children generally talk late, the right side of the brain taking on the function 

 of the left. 



Disorders of speech and voice occur from affections of the larynx, and of the 

 nerves which supply the larynx. Stammering is a want of coordination between 

 the various muscles employed in the act of speaking. 



Perhaps the most interesting of the disorders of speech, however, are 

 those associated with brain disease in adults, and to which the general 

 term Aphasia is given. There may be an entire loss of the power to 

 articulate words, or there may be a mere blurring of the speech. In other cases 

 there is a loss of memory for words, the words spoken being well pronounced, but 

 are not those which the patient wishes to utter. This is often associated with 

 Agraphia, a similar condition in respect to writing. Some writers distinguish 

 between motor aphasia, which is associated with disorganisation of the motor 

 word-centre (Broca's convolution), and sensory aphasia, in which the defect is in the 

 association of ideas of things and the ideas of their names. This is due to injury 

 of the visual word-centre, or the auditory word-centre (see p. 741), or to a severance 

 of the tracts which unite them to one another and to the motor word-centre. It 

 will readily be understood that the actual symptoms will vary greatly according to 

 the position of the lesion. It is generally admitted that injuries to the sensory 

 word-centres are more potent in the production of aphasia than injuries to Broca's 

 convolution. Marie, as already noted on p, 734, has gone so far as to assert that a 

 lesion limited to Broca's convolution will not produce aphasia, but this view has not 

 yet been fully verified. 



With regard to the auditory word-centre, impressions for the sounds of words 

 are revived in one of three ways : 



a. Spontaneous or volitional ; owing to accumulated traces which constitute 

 memory, a man when he wants to express his thoughts in words remembers the 

 sounds it is necessary to use ; impulses pass to the motor-centre (Broca's convolu- 

 tion), thence to the nerve-centres, nerves, and muscles of the larynx, mouth, chest, 

 etc. , and the man speaks. 



/>. In slight disease of the auditory word-centre, he is unable to do this, but if 

 his mind is set into a certain groove he will speak ; thus if the alphabet or a well- 

 known piece of poetry be started for him he will finish it by himself. 



<?. Mimetic. In more severe cases, a more powerful stimulus still is needed ; he 

 will repeat any words after another person, but forget them immediately afterwards. 



With regard to the visual word-centre as tested by writing, there are also three 

 ways of reviving impressions for written words or letters. 



(a) Spontaneous or normal. 



(6) A train of thought must first be set going ; as, for instance, converting 

 printed words into written characters. 



(a) Mimetic ; he can only write from a copy. 



Some operations, such as reading aloud and writing from dictation, require the 

 combined activity of several centres. This, however, we have previously considered 

 in connection with the subject of association in the brain (see p. 741). 



