64 THE CEREBRUM. 



central sulci, constituting its anterior parts, are parallel with the 

 central sulcus and are located a half or three-quarters of an inch 

 behind it, separated from the central sulcus by the gyrus centralis 

 posterior. The post-central sulci are often not continuous. The 

 inferior is about twice the length of the superior, hi this resembling 

 the central sulcus, and usually it is joined at its upper end to the 

 horizontal limb of the interparietal sulcus. The horizontal part 

 of the sulcus lies about an inch below the supero-medial border 

 of the hemisphere with which it is parallel; it separates the superior 

 parietal lobule from the inferior parietal lobule and is continued 

 as ramus occipitalis into the occipital lobe where it bifurcates. 



The posterior central gyrus reaches from the posterior limb 

 of the lateral fissure upward and backward, between the central 

 and post-central sulci, to the longitudinal fissure of the cerebrum 

 (Fig. 24). It is joined to the anterior-central gyrus around the 

 ends of the central sulcus by superficial annectant gyri (gyri 

 transitivi) and sometimes is connected with it by a buried gyrus 

 (g. profundus transitivus) which, deeply, separates the superior 

 from the inferior part of the central sulcus. The annectant 

 gyrus which closes the central sulcus superiorly and links together 

 the central gyri is the paracentral lobule (lobulus paracentralis) ; 

 the fronto-parietal part of the operculum joins them below the 

 central sulcus. The posterior central gyrus and paracentral 

 lobule constitute the receptive area of common sensation, the 

 somasthetic area, so far as it extends on the convex surface. 



The superior parietal lobule (Figs. 20 and 24) forms the 

 supero-medial border of the hemisphere from the superior post- 

 central to the occipito-parietal sulcus. It is separated from the 

 inferior parietal lobule by the horizontal part of the interparietal 

 sulcus; posteriorly, it is joined to the occipital lobe by a curved 

 annectant gyrus, called the arcus occipito-parietalis, which closes 

 the superior end of the occipito-parietal sulcus; and, over the 

 supero-medial border, it is continuous with the praecuneus of the 

 medial surface. In the praecuneus and the superior parietal 

 lobule Mills locates the stereognostic center (Figs. 56 and 57). 



The Inferior Parietal Lobule. The inferior parietal lobule 

 is incompletely divided into two or three gyri. Named from 



