666 



THE NEKVOUS SYSTEM. 



On the medial aspect of the frontal lobe there are two convolutions, the larger 

 peripheral area which forms part of the gyms frontalis superior and a smaller inner 

 part encircling the corpus callosum, which is called the gyrus cinguli. These gyri 

 are separated by the sulcus cinguli (Fig. 589). 



The posterior part of the sulcus cinguli is genetically distinct from the anterior 

 part and it circumscribes a broader area, the lobulus paracentralis, which is con- 

 tinuous with the gyri centrales of the lateral surface of the hemisphere. 



Inferior precentral sulcus 

 Inferior frontal gyrus (posterior part) I 

 Superior frontal j 



gyrus (inter- 

 Intermediate part of inferior frontal gyrus mediate part) 



Gyrus frontalis superior (anterior part) \ Sulcus 



;rior ascending ramus of lateral fissure x n diagonal! 



nterior part of inferior frontal gyrus 

 Middle frontal area 



rior horizontal 

 unus of lateral 

 :erebral fissure 



Middle frontal gyrus (posterior part) 

 Gyrus frontalis superior 

 | Superior preoentral sulcus 



| Area suprainargiualis anterior 

 I I | MOTOR CORTEX 

 I l I Sulcus postcentralis 



Sulcus centralis 



. SENSORY CORTEX 

 ' , 'Anterior part "j 



Intermediate part \ Gyrus centralis postei 

 Posterior part J 



^ Superior parietal lobule (anterior 



xSupramarginal gyrus 

 ^ Sulcus parietalis superior 

 Icus intermeuius 



Gyrus angularis 



ior parietal lobule 



I 



Superi 



. Sulcus iiiterparietalis pro 

 Lat. fis. (ascend, term. ] 

 Sulcus angulaiis 



Sulcus paroccipitalis 



Area peristriata 



Tncisura parieto- 

 ' cipitalis 



Anterior occipital 



sulcus 



Area praeoceipitali 



Area parastriat 

 ulmis occipiti 

 parauiedial 



Area fronto- 

 polaris 



Sulcus orbitalis 

 anterior ramus / 

 Area frontomarginalis 



Area proefrontalis 

 ssura orbitalis transverse limb 



Orbital area 



Area temporalis polaris 

 Sulcus temporalis anterior 



Middle temporal gyrus | 

 Middle temporal sulcus 

 \ Inferior temporal gyrus 

 Pars circuinambiens (superior temporal gyrus) 



Sulcus retrocalcarinut 

 AREA BTRIATA 



Sulcus lunatus (sulcus simialis) 

 Sulcus occipitalis lateralis 

 Area praeoccipitalis 

 Area occipitotemporalis 

 ulcus temporalis superior 

 AREA ACUSTICA 

 I Area subcentralis 

 Pars intermedia (superior temporal gyrus) 



FIG. 594. AREAS ON LATERAL ASPECT OF LEFT CEREBRAL HEMISPHERE. 



The superior, middle, and inferior frontal sulci are not labelled. The middle is in the midst of the green 

 area, the superior and inferior respectively at its superior and inferior boundaries. 



On the orbital aspect of the frontal region there are two sulci, viz., the olfactory 

 and the orbital. 



The olfactory sulcus is a straight furrow which runs parallel to the medial orbital 

 border of the hemisphere. It is occupied by the olfactory tract and bulb, and it 

 cuts off a narrow strip of the orbital surface close to the medial border, which 

 receives the name of gyms rectus. 



The orbital sulcus is a composite furrow which assumes many different forms. 

 It consists essentially of a U-shaped furrow, the convexity of which is directed 

 anteriorly (Fig. 585), and one or two variable branches passing forwards from it. 



The conventional manner of subdividing the cortical territory anterior to the 

 sulcus centralis into gyri, which -has just been sketched, is apt to convey a mis- 

 leading idea of the distribution of the anatomical areas of differentiated cortex. 



The gyrus centralis anterior together with the major portion of the paracentral 

 lobule and the posterior part of the middle and superior frontal gyri form a natural 

 subdivision of the cortex, which Brodmann calls the regio prsecentralis. It is com- 

 posed of a series of areas of different structure, which may be grouped as the area 

 prsecentralis posterior (the true motor area), the area prsecentralis intermedius, and 



