GENERAL FEATURES 361 



Portions of four of the lobes, the frontal, the parietal, the 

 occipital and the temporal, are visible on the supero-lateral 

 surface. 



The frontal lobe lies anterior to the central sulcus and 

 above the stem and the anterior part of the posterior ramus of 

 the lateral fissure. In it, immediately anterior to the central 

 sulcus, is the anterior central gyrus, in which is the motor 

 area of the cerebral cortex (Fig. 153). The anterior central 

 gyrus is partially separated from the more anterior part of the 

 frontal lobe by a precentral sulcus, which is generally divided 

 into upper and lower portions. Anterior to the pre-central 

 sulcus there are three gyri which run antero-posteriorly ; they 

 are named from above downwards, the superior, middle, and 

 inferior frontal gyri (Figs. 135, 137). 



The dissector should note (i) that the anterior horizontal 

 and anterior ascending rami of the lateral fissure cut into the 

 inferior frontal gyrus; and (2) that, whilst the frontal lobe is 

 partly covered by the frontal bone, a considerable part of its 

 posterior portion, including the anterior central gyrus and 

 the posterior parts of the antero-posterior gyri, is under cover 

 of the anterior part of the parietal bone (Fig. 177). 



The parietal lobe is bounded, anteriorly, by the central 

 sulcus ; posteriorly, by the parieto-occipital fissure and a line 

 prolonged from it to a notch (Fig. 135) on the infero-lateral 

 border called the pre-occipital notch \ inferiorly, by the posterior 

 ramus of the lateral fissure, and a line prolonged backwards 

 from the point where that fissure turns from a horizontal to a 

 vertical direction to the line from the parieto-occipital fissure 

 to the pre-occipital notch. The supero-lateral surface of the 

 parietal lobe is separated into three main areas. Immediately 

 posterior to the central sulcus is the posterior central gyrus. 

 It is bounded, posteriorly, by the post-central sulcus, and it is 

 the region of ordinary sensation (Fig. 153). Behind the 

 post-central sulcus the parietal lobe is separated into an upper 

 and a lower parietal lobule, by an antero-posterior sulcus called 

 the sulcus interparietalis proprius. 



The occipital lobe lies behind the parieto-occipital fissure 

 and the line which connects that fissure with the pre-occipital 

 notch. Its surface is divided into four areas by three sulci. 

 The area in the region of the occipital pole is marked off by 

 a curved sulcus, concave backwards, called the sulcus lunatus. 

 The larger anterior part is divided by two antero-posterior 



