THE PARIETAL REGION IN THE PRIMATE BRAIN 



N. W. IXGALLS 



From the Laboratories of Anatomy of The University, Manchester , England, and of 

 Western Reserve University, Cleveland 



NINETEEN FIGURES 



During the last ten years the problems of the interpretation of 

 the cerebral sulci and of the various areas into which they divide 

 the cortex have come to be regarded from a new point of view. 

 The mass of detailed observations concerning the structural lo- 

 calization of the cortex which has been accumulated renders it 

 necessary, therefore, to reexamine these sulci in the light of this 

 new information and to determine, as far as may be possible, 

 what meaning is to be attached to the detailed findings of Vogt, 

 Brodmann, Mauss and many others. 



It is eminently desirable that such an inquiry should be under- 

 taken in order that the facts of anatomical localization may be 

 correlated with the varying pattern of the convolutions. This is 

 all the more necessary because much of our information concern- 

 ing cerebral localization has been collected by investigators who 

 have minimized or even denied the influence of localization in de- 

 termining the arrangement of the cerebral sulci. Our knowledge 

 at present is, however, sufficient to indicate that the distribution 

 of the differentiated cortical areas is the chief factor in determin- 

 ing the development of sulci in definite situations, either along 

 the boundaries of areas or in the axis of a given area. 



In this communication I propose to study the parietal region and 

 the areas adjoining it in the light of this new knowledge. More 

 especially will it concern itself with the changes produced in the 

 inferior parietal area, changes which result from the enormous 

 expansion and differentiation of this area during the transition 

 from the simian to the human condition. 



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