THE ( '1:1! EIUIA I. // /v'.U /.s'/ 



Ml 



represents the third of the primary furrows, is continual backwards past the superior 

 (\ttvmily of the parietO-OCCipital fissure into the occipital lobe, where it usually 

 joins I lie' (icci/iitnl nuiiiix. the fourth of the primary furrows. This rainus divides 

 shortly into two branches which run at riliht angles t.. the stem, torinini: the tNUU- 

 gent occipital Kiilctis. and thus arises the transverse l.ar of the posterior end of the 

 interpanetal sulcus. The occipital rainus may, however, consist of little more than 

 the transverse liar, which may or may not he joined by the hori/.onlal ratlins. The. 

 occipital ramus is more frequently separate from the horizontal than is the post- 

 cm! nil sulcus. In their development the inferior post cent nil sulcus appears first, 

 (diiriiiir I lie latter part of the six! h month), the occipital ramus second, the horizontal 

 ramus third, and last . t he superior post rout nil sulcus. 



The superior parietal lobule (gyrus) is the area of the supero-mesial border 

 of the parietal lobe. It is limited in front by the superior postcentral sulcus, below 

 by the hori/.ontal ramus of the interparietal sulcus, and posteriorly it is continuous 



Fiu 0:2.5. CONVEX SURFACE OF THE CEREBRAL HEMISPHERES AS VIEWED FROM ABOVE. 

 (After Toldt, "Atlas of Human Anatomy," liiM.inaii, I-ondon and New York.) 



rr.nsTM. /<//./. 



SUPERIOR BORDER 



- Laxnrrrnix.il. 

 FISSURE 



FRONTAL 8ULCV& 



- PHWESTRAL 



AJ icua 



SM^ 



1NTERPARIETM, 

 SULCUS 



PARIETO-OCCIPITAL 



h'lXHVRK 



SUPERIOR OCCIPITAL SVLCI 

 CCIPITAL POLE 



around the superior end of the parieto-occipital fissure into the cortex of the occipital 

 lobe. It is a relatively wide area (lobule), always invaded by collateral twigs of its 

 limit in; sulci, and usually contains a few short, isolated furrows. When the parieto- 

 occipital fissure is considerably prolonged over the supero-mesial border (external 

 piirittii-occijiildl /ixftun-), the continuation of the lobule about the end of this fissure 

 presents the appearance described as the parieto-occipital arch. 



The inferior parietal lobule is limited in front by the inferior postcentral sulcus, 

 and above by the horizontal ramus of the interparietal sulcus. It is continuous with 

 the cortex of the temporal lobe below, and with that of the occipital lobe behind, and 

 is therefore invaded by the ends of the sulci lielonj;in<; to these lobes. Its anterior 

 portion is separated from the temporal lobe by the hori/oiital portion of the posterior 

 ramus of the lateral fissure. The upturned end of this ramus invades the anterior 

 portion of the lobule and the broad fold, arched around this end and continuous 

 behind it into the superior temporal jryrus, is known as the supramarginal gyrus. 



