SENSE AREAS AND ASSOCIATION AREAS. 223 



along the margins of the posterior portion of the lateral fissure 

 (fissure of Sylvius), and extending into the parietal lobe as far as 

 the angular gyrus, and with the cortex within the fissure including 

 the cortex of the island. 



The general facts regarding aphasia illustrate very well the 

 theory or idea usually held among physiologists in regard to the dis- 

 tribution or localization of mental activity in the cerebral cortex. 

 The understanding and the use of spoken or written language is, so 

 to speak, a mental whole, both from the standpoint of education 

 and of use. To understand or to express certain conceptions im- 

 plies the use of definite words, and our visual, auditory, and motor 

 experiences are combined in these symbols. Each phase of this com- 

 plex may be cultivated more or less separately; in the case of the 

 unlettered man, for instance, the written or printed symbols form 

 no part in the associations connected with his verbal concepts. Cor- 

 responding to these facts we have, on the anatomical side, a portion 

 of the brain in which the auditory memories are organized, that 

 is, they are connected in some way with a definite arrangement 

 of nerve cells and their processes, another part in which the 

 visual memories are organized, and other parts in which the 

 motor memories as regards speaking or writing are laid down 

 in some definite form. Each part is a distinct center, but 

 their combined use in intellectual life would imply that they 

 are connected by association fibers, so that, although fun- 

 damentally distinct, they are practically combined in their 

 activity. Corresponding with this conception it is found from 

 clinical experience that sensory aphasics suffer a deterioration, 

 more or less pronounced, of their general intellectual capacity 

 according to the extent of the area involved. We may believe 

 that the varying gifts of individuals, in the matter of the use of 

 language, rest partly on the amount of training received and 

 partly on the inborn character and completeness of the nervous 

 machinery in the different centers. 



The Association Areas. According to the views presented 

 above, it will be seen that the motor and sense areas occupy only 

 a small portion of the cortex, forming islands, as has been said, 

 surrounded by much larger areas. Flechsig* has designated these 

 latter areas as association areas, and has advocated the view that 

 they are the portions of the cortex in which the higher and more 

 complex mental activities are mediated, the true organs of thought. 

 His views as to the relations and physiological significance of these 

 areas have been based chiefly on the study of the embryo brain 

 with reference to the time of acquisition of the myelin sheaths. 



* Flechsig, "Gehirn und Seele," Leipzig, 1896; also, " Archives de Neurol- 

 ogic," vol. ii, 1900. 



