762 VOICE AND SPEECH [CH. LV. 



If a child becomes deaf before it is six or seven years old, there is a liability it 

 will forget the speech it has learnt, and so become dumb. 



In congenital hemiplegia there may be speechlessness, especially if the injury is 

 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 co-ordination between 

 the various muscles employed in the act of speaking. 



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

 to brain disease in adults. These fall into three principal categories : 



1. Aphemia. A difficulty or inability to utter or articulate words. It is often 

 associated with difficulty of swallowing, and occurs in lesions of the base of the 

 brain, especially of pons and bulb. The blurring of speech noticed in most cases of 

 apoplexy may also be included under this head. 



2. Aphasia. This is a complex condition in which the will to speak exists, and 

 also the ability to speak, but the connection between the two is broken down. 

 When the patient speaks, the words which he utters are well pronounced, but are 

 not those he wishes to utter. This is often associated with Agraphia, a similar 

 condition in respect to writing. It is the form of disordered speech associated with 

 disorganisation of Broca's convolution. 



3. Amnesia. This term includes a krge class of cases in which the main 

 symptom is loss of memory for words, or a defect of the association of ideas of 

 things with ideas of words, not, as in aphasia, with ideas of verbal action. Amnesia 

 is associated with lesions of the intellectual, .<?., the sensory centres of the cortex 

 behind the Rolandic area. We have seen that in this region of the brain there are 

 two important centres, the visual and the auditory, and the parts of these which are 

 associated with words may be called the visual word-centre and the auditory word- 

 centre. In amnesia (sometimes called sensory aphasia), either these centres them- 

 selves, or the tracts that connect them, are diseased or broken down. See also 

 p. 695. 



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. 



b. 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. 



c. 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. 



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

 printed words into written characters. 



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



Two operations require the combined activity of both centres ; the first of these 

 is reading aloud, the second is writing from dictation. These, however, we have 

 previously considered in connection with the subject of association in the brain 

 (seep. 695). 



In the investigation of any case of defective speech there are always the follow- 

 ing six things to be inquired into : 



1. Can the patient understand spoken words? (The patient, of course, not 

 being deaf.) If he cannot, the auditory word-centre is deranged. 



2. Can he repeat words when requested ? This tests the emission fibres from 

 the auditory word-centre which pass through the motor-centres for speech in Broca's 

 convolution. If he cannot do this, the patient has aphasia. 



