654 



THE NERVOUS SYSTEM. 



the parietal tuberosity of the cranial wall by turning upwards* into the parietal 

 region in the form of an ascending terminal piece. 



The anterior horizontal ramus extends horizontally forwards in the frontal region 

 for a distance of not more, as a rule, than three-quarters of an inch, immediately 

 above and parallel to the posterior part of the superciliary margin of the hemisphere. 



The anterior ascending ramus proceeds upwards and slightly forwards, into 

 the inferior part of the lateral surface of the frontal region for a variable distance 

 (an inch or less). In many cases the two anterior limbs spring from a common stem 

 of greater or less length, and not infrequently there is only a single anterior limb. 



Sulcus Circularis. If the lips of the posterior ramus of the lateral fissure are 

 pulled widely asunder from each other, the insula (island of Eeil) will be seen at the 



Inferior frontal gyrus (posterior part) 

 Superior frontal 

 gyrus (inter- 



itermediate part of inferior frontal gyrus mediate part) 

 3yrus frontalis superior (anterior part) \ Snlcus ' 



.r ascending ramus of lateral fissure v . diagonals I 



ior part of inferior frontal gyrus 

 Middle frontal area 



horizontal 

 is of lateral 

 ibral fissure 



r frontal 

 area 



Inferior precentral sulcus Middle frontal gyrus (posterior part) 



Gyrus frontalis superior 

 | Superior precentral sulcus 

 j | Area supramarginalis ; 

 MOTOR CORTEX 



Sulcus postcentndis 



Sulcus centralis 



KNSORY 



ORTEK 



Anterior part "| 



Intermediate part [ Gyrus centralis posterioi 

 Posterior part J 



Superior parietal lobule (anterior 

 part) 



upramarginal gyrus 

 Icus parietalis superior 



ulcus intermedius 

 Gyrus angularis ipui 



~uperior parietal lobule (pos 

 ulcus iuterparietalis propri 

 Lat. fis. (ascend, term, piei 

 Sulcus angularis 



Sulcus paroccipitalis 



Area peristriata 



ncisura parieto- 

 / occipitalis 



^rea fron 



polaris 



Sulcus orbitalis , 



(anterior ramus) ' 



irea frontomarginalis 



Area prjefrontalis 

 \ orbitalis (transverse limb) 



Orbital area 



Area temporal! s polari 

 Sulcus temporalis anterior 



Middle temporal gyrus | 

 Middle temporal sulcus 



Inferior temporal gyrus 

 Pars eirenmambiens (superior temporal gyrus) 



ulcus retrocalcarinus 

 AREA STRIATA 



^ulcus lunatus (sulcus simialis) 

 I Sulcus occipitalis lateralis 

 Area praeoccipitalis 

 occipitotemporalis 

 I Sulcus temporalis superior 

 AREA ACUSTICA 

 I Area subcentralis 

 Pars intermedia (superior temporal gyrus) 



FIG. 581. A DIAGRAM OF THE LATERAL ASPECT OF THE LEFT CEREBRAL HEMISPHERE. 



The inferior frontal sulcus (the superior boundary of the inferior frontal gyrus), the middle frontal sulcus 

 (separating the anterior and middle frontal areas), and the superior frontal sulcus (bounding the superior 

 frontal gyrus) are not labelled. 



bottom. The insular district of the cortex is completely hidden from view, when 

 the lateral fissure is closed, by overlapping portions of the cerebral hemisphere, 

 and, when brought into view in the manner indicated, it is observed to present a 

 triangular outline and to be surrounded by a limiting sulcus, of which three parts 

 may be recognised, viz., a superior part, bounding it above and separating it from the 

 parietal and frontal regions ; an inferior part, marking it off below from the temporal 

 region ; and an anterior part, separating it in front from the frontal region. 



The insula consists of three areas of different structure. At the antero-inferior 

 corner (where the sulcus circularis is deficient) the knee-like bend of the area 

 piriformis (see Figs. 582 and 584) appears at the limen insulse. The rest is subdivided 

 by an oblique furrow (sulcus centralis insulse) into a posterior part divided into 

 gyri longi and an anterior part divided into gyri breves. 



