vm] Parietal Area 203 



Special remarks are called for concerning the structure of that portion of the superior 

 parietal gyrus lying immediately anterior to the upper extremity of the parieto-occipital 

 fissure, because it is one which has been recently singled out by Flechsig for special 

 description. Overlooked in his earlier observations, Flechsig now asserts that this part takes 

 a high position in the myelogenetic sequence and he numbers it 14 instead of 22, as he 

 did in 1!K>1. He further distinguishes the field by the name " supraangular," on account 

 uf its relation to the angular gyrus. 



Now it seems to be a fundamental rule, that those parts of the cortex which receive 

 their medullated fibres at an early date are exactly those which harbour a great wealth 

 of fibres of large calibre; they thus prove interesting fields for examination in the adult brain, 

 because their boundaries are easily determined and their structure usually departs from the 

 common plan. For this reason I have been attracted to this part and have examined it 

 most carefully in a number of brains, but unfortunately my conclusions do not altogether 

 harmonise with those of Flechsig, and in particular I object to granting independence to his 

 "supraangular" field. What I would say is that the structure here is subject to variation, 

 in some cases it is endowed with a great wealth of fibres, and in others it shows the ordinary 

 " parietal " formation. Then in those instances in which the fibre supply is great, on tracing 

 the area backward, it can always be found to be continuous with the field of cortex to which 

 I have given the name " visuo-psychic," indeed the type of arrangement it presents is actually 

 the " visuo-psychic " type ; hence I maintain that in these cases we have merely to deal 

 with a forward extension of the visual area 1 . But what the cause of the variation in 

 distribution is, I am not at the present prepared to say ; I am, however, under the impression 

 that variations in depth and extent of sulci situated hereabout, in particular the parieto- 

 occipital fissure and the ram us occipitalis transversus of Ecker, are not unimportant. 



In further substantiation of my statement that in these cases we have to deal with 

 a forward prolongation of the " visuo-psychic " area, I would add that an examination of the 

 cell lamination fully bears it out, for the superiority in fibre wealth is invariably associated 

 with the presence of those curious large pyramidal cells for which I have claimed so much 

 attention, and in short with a " visuo-psychic " type of lamination. Furthermore, in the 

 anthropoid ape the same area is subject to similar variations, and in this animal the 

 distribution seems to be distinctly influenced by the position of the upper extremities of the 

 parieto-occipital fissure and the " Affenspalte." 



Other sub-areas made out by Flechsig are undefinable in the fully-developed brain. 



DISTRIBUTION OF THE PARIETAL AREA. 



As may be gathered from what has been already said, the " parietal " area may be 

 briefly described as covering the precuneus, the superior parietal gyrus, and the anterior 

 part of the supramarginal gyrus. 



Concerning boundaries on the mesial surface of the hemisphere, the upturned tail of the 

 calloso-marginal fissure, and the parieto-occipital fissure may be looked upon as constant anterior 

 and posterior limits. Interiorly it comes into relation with the limbic area, and the line of 



1 Anatomically the part in question is nothing more than the superior parieto-occipital annectant gyrus, the gyrus 

 which arches round the upper extremity of the parieto-occipital n'ss'ure, and one which we know is inconstant in 

 size anil position. 



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