314 THE NERVOUS SYSTEM 



clinical evidence to support this view. Cases have been 

 described in which the spoken word is not understood 

 (word-deafness). In these cases reading may not be 

 impaired; the motor functions of speech may not be 

 seriously disturbed. The loss of speech is due to an 

 inabihty to hear and to form mental (auditory) images 

 of words. This is one form of sensory aphasia. It is 

 associated with a lesion of the temporal lobes. Cases of 

 word-blindness also occur, but these are not associated 

 with aphasia to the same extent, since auditory images 

 are more important than visual images for speech. 



The inabihty to write when it is unaccompanied by 

 paralysis of other hand movements is known as agraphia. 



The close connection which exists between speech and 

 the more complex mental processes is shown by the fine 

 distinctions in the disabihty found among different sufferers 

 from aphasia. Some cannot state the names of objects, 

 others cannot describe what the objects are for ; in others 

 there are certain particular words which have dropped out 

 of their vocabulary. Others, again, are capable of emotional 

 but not of intellectual expression. 



LOCATION OF THE HIGHER PSYCHICAL PROCESSES 



In its higher psychical function the cerebrum seems to 

 act as a whole, the claims of the phrenologist being without 

 scientific foundation.' The only suggestion that any kind 

 of locahsation prevails comes from the examination of 

 people suffering from injuries to the frontal lobes. Such 

 patients often show a curiously facile behaviour, and seem 

 to have lost the capacity for taking things seriously. 



7.— THE FUNCTIONS OF THE CEREBRUM 



The dominance of the cerebrum over the rest of the 

 nervous system increases as we rise in the animal scale. 



