878 



THE NERVOUS SYSTEM 



from the posterior end of the spheno-parietal suture along the anterior part of the squamo- 

 parietal suture to its highest point; thence it continues in the same direction beneath the parietal 

 bone towards the lambda, terminating either in front of or below the parietal eminence. In 

 the child, however, the fissure is considerably above the line of the squamo-parietal suture (fig. 

 652), which it gradually approaches, attaining its adult position about the ninth year. This 

 change of position, which occurs during the first nine years, is due partly to the ascent of the 

 sutunil line and partly to the descent of the fissure on the surface of the brain. 



The frontal bone always covers the superior, middle, and inferior frontal gyri, except their 

 posterior extremities, which are beneath the parietal bone (fig. 651). The ascending limb (ramus 

 anterior ascendens) of the lateral fissure, which cuts into the posterior part of the inferior frontal 

 gyrus, runs parallel with and under cover of the lower part of the coronal suture, or immediately 

 in front of it, and the anterior horizontal limb is parallel with and beneath the upper margin of the 

 great wing of the sphenoid. The parietal bone is in relation with the convex surfaces of four 

 lobes of the brain. Speaking very generally, it may be said that the anterior third covers the 

 posterior part of the frontal lobe, including the anterior central gyrus, and the posterior ends 

 of the superior, middle, and inferior frontal gyri and the precentral sulcus. The posterior two- 

 thirds are superficial to the parietal lobe, the posterior part of the temporal lobe, the anterior 

 part of the occipital lobe, the posterior part of the horizontal limb of the lateral fissure, the upper 

 and lower parts of the post-central sulcus, the interparietal sulcus, the posterior sections of the 

 superior and middle temporal sulci, and the external part of the parieto-occipital fissure. The 



Fio. 652. DRAWING OP A CAST OP THE HEAD OP A NEWLY BORN MALE INFANT. 

 (Prepared by Professor Cunningham to illustrate cranio-cerebral topography.) 



INTERPART- 

 ETAL SULCUS 

 EXTERNAL 

 PART OF 

 PARIETO- 

 OCCIPITAL 

 FISSURE 



CENTRAL 

 SULCUS 

 (KOLANDI) 



POSITION OF PARIETAL 



EMINENCE 

 POSITION OF FRONTAL 



EMINENCE 



central sulcus is beneath the parietal bone at the junction of its middle and anterior thirds (fig. 

 651). 



In the adult, the upper end of the central sulcus lies 55 per cent, of the whole length of the 

 naso-inionic line behind the nasion. It is 55 mm. from the coronal suture in dolichocephalic, and 

 54'4 mm. in brachycephalic, heads. The lower end of the sulcus, which is immediately above 

 the posterior horizontal limb of the lateral fissure, lies beneath the point of intersection of the 

 auriculo-bregmatic line with a line drawn from the stephanion (the point where the temporal 

 ridge cuts the coronal suture) to the asterion. In skulls of a sagittal length of 18 cm. and over, 

 this point is 45'5 per cent, of the horizontal arc from the glabplla to the inion, and in skulls of less 

 than IS cm. it is 46 per cent, of the same arc posterior to the glabella. 



The upper end of the parieto-occipital fissure usually lies about 5 mm. in front of the lambda, 

 and the course of the fissure may be indicated by a line drawn from 5 mm. in front of the lambda 

 to a point immediately above the asterion, and. as the latter point corresponds with the pre- 

 occipital notch on the infero-lateral border of the hemisphere, the line in question will indicate 

 the adjacent margins of the parietal, temporal, and occipital lobes. 



The occipital bone is in close relation with the cerebellum, as already pointed out, but it 

 also covers the posterior part of the outer surface of the occipital lobe of the cerebral hemisphere. 

 The great wing of the sphenoid covers the outer surface of the apex of the temporal lobe, and the 

 squamous part of the temporal bone covers the anterior parts of the superior, middle, and inferior 

 temporal gyri and the sulci which separate them. 



