324 NEUROLOGY, OR ANATOMY OF NERVOUS SYSTEM 



parietal lobe, also the paraoccipital and exoccipital fissures are 

 seen extending into the lobe. ' 



The mesal surface presents the cuneus embraced by the 

 occipital and calcarine fissures; a small fissure is seen near the 

 posterior third of this surface, and is called the cuneal. 



The temporal lobe, the lateral surface is bounded by the basi- 

 sylvian and Sylvian fissures and by the ventrolateral border; 

 posteriorly, it merges into the adjacent parietal and occipital 

 lobes. The gyre are the supertemporal, the meditemporal, and 

 subtemporal. The fissures are the supertemporal and medi- 

 temporal. 



The tentorial or ventral surface of the temporal lobe: The 

 gyre are the subcalcarine, the subcollateral, and part of the 

 subtemporal; near the dorsimesal part of the ventral surface 

 is found the hippocampal, and the uncinate gyre is found 

 toward the temporal pole. The fissures are the subtemporal, 

 collateral, and the occipitocalcarine stem, the hippocampal, and 

 the postrhinal. 



The dorsal or opercular surface of the temporal lobe enters into 

 the formation of the Sylvian cleft. The transtemporal fissures 

 and transtemporal gyres are found upon this surface. 



The island of Reil (central lobe or insula) is seen after separating 

 the lips of the Sylvian cleft, and is overlapped by the opercula; 

 the latter removed, the island of Reil is seen as a tetrahedral- 

 shaped mass with its apex directed ventrocephalad. Its borders 

 are sharply outlined by the circuminsular fissure, except in 

 the depths of the basisylvian cleft, where the insular cortex 

 is continuous with the gray substance of the anterior per- 

 forated substance or lumen insulse (belonging to the rhin- 

 encephalon). The transinsular or central fissure divides this 

 area into a larger preinsular and a smaller postinsular part. 

 The preinsular shows four to five preinsular gyres ; the postinsular 

 presents a single long gyre (the gyrus longus insulre). 



The rhinencephalon, or olfactory lobe, constitutes the central 

 olfactory structures, as distinguished from the rest of the 

 fore-brain (pallium). It comprises: (1) Peripheral parts; 

 (2) central or cortical portions; the former is divided into 

 pre- and postolfactory portions. 



