THE VISUAL AEEAS AND FIBKE-TKACTS. 



661 



make their appearance relatively early in development and become very deep 

 furrows. 



The inferior of these is placed upon the tentorial surface, and is known as the 

 sulcus collateralis ; the superior limiting furrow of the visual territory (its peristriate 

 part) is upon the superior surface of the hemisphere, and is usually regarded as the 

 ramus occipitalis of the sulcus interparietalis. But it is genetically independent of 

 the latter furrow, and may be distinguished as the sulcus paroccipitalis. 



Near the super o- medial margin of the hemisphere there is a furrow, which 

 indicates the line of demarcation between the para- and the peristriate areas the 

 sulcus occipitalis paramedialis. It may be situated upon either the medial or the 

 superior surface of the hemisphere. In some cases it belongs to the category of 

 limiting sulci, in others to the group of operculated sulci (see p. 646). 



Lobulus paracentralis 

 Sulcus cinguli | 



Superi 



Gyrus cingul 



frontal gyrus (posterior part) \ 



Corpus callosum \ \ 



Superior frontal gyrus (intermediate part; 



perior frontal gyrus (anterior part) 



Gyrus cinguli 

 Sulcus cinguli 

 Area paracingularis 

 Icus paracingularis 

 ior frontal area 



Sulcus paracentralis 

 I Sulcus subparietalis 

 Parasplenial area 

 Sulcus ceiitralis 



Incisura sulci cinguli 



Praecuueus (anterior part) 

 Sulcus prsecunei 



Praecuneus (posterior part) 

 Sulcus parieto-occipitalis 



Incisura parieto-occipits 



rea peristriata 

 i Sulcus polaris su 



Area frontopolar 



Sulcus rostrali 



Area praefrontalis i 



Sulcus subrostralis 



Area temporalis polaris* 



Gyrus cinguli 

 Fissura rhlnalis 



Piriform area 

 Gyrus temporalis inferior 



Junction of 



| / ,| | Sulci limitantes areee striatse 

 tategyri, I Sulcus collateralis 



which form Area occipito temporalis 



one area I Area parastriata 



Sulcus calcarinus' 



Icus calcari 

 lateralis 



| Sulcus polaris inferior 

 Area striatu 



ileus calcarinus posterior 

 Area peristriata 



FIG. 589. THE CORTICAL AREAS ON THE MEDIAL ASPECT OF THE CEREBRAL HEMISPHERE. 



Passing horizontally forwards upon the lateral surface of the hemisphere there 

 is a constant furrow formed by the axial folding of part of the peristriate area, 

 approximately in line with the axial folding of the striate area (sulcus cal- 

 carinus lateralis) ; it is the sulcus occipitalis lateralis. When there is a fully 

 developed sulcus lunatus the lateral occipital sulcus joins it near its midpoint 

 (Fig. 581, p. 654). 



The sulcus (or fossa) parieto-occipitalis (Fig. 554) is usually a deep furrow upon 

 the medial aspect of the hemisphere which passes vertically downwards from the 

 supero-medial border and appears to join the calcarine sulcus near its union with 

 the posterior calcarine, forming upon the surface a Y-shaped pattern, the stem of 

 which is calcarine, the limbs posterior calcarine and parieto-occipital respectively, 

 and the wedge-shaped area between the limbs the cuneus (Fig. 588 ; compare with 

 the pattern shown in Fig. 589, where the parieto-occipital sulcus is not labelled). 



If, however, the lips of these three furrows are divaricated (Fig. 588), the parieto- 

 occipital depression will be found to be separated from the calcarine by a prominent 



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