vra] Parietal Area 207 



A question which has formed the subject of a considerable amount of debate is that 

 concerning the relative size of the parietal lobe in man and in the mammalian series, and it 

 is now virtually decided that a high development of this lobe is one of the most important 

 superior characteristics of the human brain. Taking this for granted the point does not 

 help us in settling its function, but whatever this be, the existence of a homologous area 

 practically throughout the phylogenetic mammalian series makes it certain, or at least extremely 

 probable, that the function likewise has its representation. 



SUMMARY. 



1. The term "parietal" is being applied to an area which may be briefly described 

 as covering the precuneus, the superior parietal gyrus, and the anterior part of the supra- 

 marginal gyms. 



2. Structurally its cortex possesses all the cell laminae of and a similar arrangement of 

 nerve fibres to the " intermediate postcentral " area, but it differs in containing a smaller 

 number of special large pyramidal cells and of large medtillated nerve fibres ; it is also peculiar 

 in showing a more perfect reduplication of the line of Baillarger. 



3. In the adult brain no important topical variations can be defined in the area. The 

 richness in nerve fibres of the superior parieto-occipital annectant gyrus (Flechsig's supraangular 

 area) has been noticed, but only occasionally and then in association with a forward extension 

 of the " visuo-psychic" area, of which it forms a part. 



4. A similar cortical formation in and distribution of this area obtain in the anthropoid 

 ape, but the field suffers a reduction in extent in the region of the precuneus. 



5. A homologous area can be traced phylogenetically throughout the vertebrate series. 



6. To electrical excitation the area is irresponsive, and histology seems to favour the 

 clinical doctrine that it shares with the " intermediate postcentral " cortex the function of 

 elaborating complex impressions embodied in the muscular and stereognostic senses. Here, 

 however, the localisation of the higher faculty of which sensations are the essential basis, 

 consciousness, has to be borne in mind, but being wrapt in speculation this difficult question 

 is not entered into. 



REFERENCES. 



THEODOR KAES. Beitrage zur Kenntniss des Reichthums der Groashirnrinde des Menschen an 

 markhaltigen Nervenfasern. Archiv f. Psych, u. Nervenkr., Band xxv, Heft .3, 1893. 



CARL HAMMARBERG. Loc. cit. 



P. FLECHSIG. Developmental (myelogenetic) Localisation of the Cerebral Cortex in the Human 

 Subject. Lancet, Vol. n, p. 1027, 1901. Other papers already quoted. 



O. and C. VOGT. Loc. cit. 



C. VON MONAKOW. Loc. cit. 



