CEREBRAL LOCALIZATION OF FUNCTION. 



213 



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

 tient 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. 



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-deaf- 

 ness the patient can not 

 understand vocal speech, 

 though he is capable of 

 hearing other sounds. 

 This condition is associ- 

 ated with lesion of the 

 first temporal convolution. 

 In word-blindness the pa- 

 tient 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. 



Figure 29 will illustrate 

 the conditions in the 

 various forms of aphasia. 



Impressions are constantly passing from eye and ear to the visual 

 and auditory centers and are there being registered. Commissural 

 fibers connect these centers with the arm and speech centers, which 

 in turn are connected by efferent fibers with the muscles of the hand 

 and of the vocal apparatus. Muscular movements of the eye, hand, 

 and mouth are also registered by means of the afferent fibers, s, s', s". 



FIG. 29. 



