CEREBRAL LOCALIZATION OF FUNCTIONS. 1 91 



Lesions of the third frontal convolution on the left side, if the patient be 

 right-handed, produce the various forms of aphasia, or the partial or complete 

 loss of the power of articulate speech. 



Aphasia is of many degrees and kinds. In ataxic aphasia the patient is 

 unable to communicate his thoughts by words, there being an inability to 

 execute the movements of the mouth, etc., necessary for speech. In agraphic 

 aphasia there is an inability to execute the movements necessary for writing, 

 though the mental processes are retained. In the ataxic form the lesion is 

 in the third frontal convolution, and in the agraphic form it is in the arm 

 center. 



FIG. 30. THE AREAS AND CENTERS OP THE MESIAL ASPECT OP THE HUMAN 

 HEMI-CEREBRUM. (C. K. Mills.) 



In amnesic aphasia there is a loss of the memory of words, the purest exam- 

 ples of which consist of the affections known as word-deafness and -word- 

 blindness. In word-deafness the patient can not understand vocal speech, 

 though he is capable of hearing other sounds. This condition is associated 

 with lesion of the first temporal convolution. In word-blindness the patient 

 can not name a letter or a word printed or written, though he can see all 

 other objects. This condition is associated with impairment of the visual 

 centers. 



