CRANIO-CEREBRAL TOPOGRAPHY. 7 



and its lower end about 3 cm., behind the coronal suture. The superior precentral 

 sulcus is from 2 to 3 cm. behind the upper part of the coronal suture ; and the 

 inferior precentral sulcus is a short distance (1 to 2 cm.) behind the lower part of 

 the same suture. The inferior frontal sulcus about corresponds to the stephanion 

 and the temporal crest of the frontal bone. The intraparietal fissure is very variable 

 in position : its ascending or postcentral portions are approximately parallel to and 

 about 15 mm. behind the fissure of Kolando ; while its longitudinal portion runs 

 backwards, with a slight inclination inwards, just above the parietal eminence, and 

 at an average distance of 45 mm. from the median line anteriorly, 35 mm. 

 posteriorly opposite the lambda. The parallel fissure lies mainly beneath the upper 

 part of the squamous and the hinder part of the temporal area of the parietal bone, 

 but its posterior end crosses the temporal lines and runs upwards for a short distance 

 in the parietal lobe of the hemisphere under the superior division of the parietal 

 bone : its position in the temporal part of its extent is indicated approximately by a 

 line drawn from the marginal tubercle of the malar bone to the lambda. In the 

 child, owing in great measure to the relatively small size of the squamous part of the 

 temporal bone, the parallel fissure appears to be placed much higher, often reaching 

 the level of the squamous suture. 



From the foregoing determination of the situation of the fissure of Kolando and 

 precentral sulci, it follows that the ascending frontal and the bases of the upper, 

 middle, and lower frontal convolutions are placed beneath the anterior third of the 

 parietal bone. The main parts of the superior and middle frontal convolutions 

 correspond to the frontal region of the frontal bone, and of this area the superior 

 frontal convolution may be said to occupy rather less than the inner half, and the 

 middle frontal convolution rather more than the outer half. The centre of the 

 frontal eminence is commonly over the middle convolution. The apex of the pars 

 triangularis of the inferior frontal convolution corresponds to the antero-inferior 

 angle of the parietal bone ; and the pars orbitalis is covered by the temporal division 

 of the frontal bone and the upper end of the great wing of the sphenoid. The 

 whole of the parietal lobe is under cover of the parietal bone, the parietal eminence 

 corresponding to some part of the supramarginal convolution ; while the occipital 

 lobe occupies the cerebral division of the occipital bone, and sometimes extends slightly 

 beneath the adjacent part of the parietal bone. The temporal lobe lies for the most 

 part beneath the squamous division of the temporal bone and the postero-inferior fourth 

 of the parietal bone, its superior convolution being marked off from the rest by the line 

 given above for the parallel fissure ; but the anterior extremity of this lobe projects 

 under the great wing of the sphenoid, while posteriorly the inferior temporal convolu- 

 tion is prolonged beneath the occipital bone to the occipital pole of the hemisphere. 



Determination of the principal fissures on the surface of the head. If a median 

 line be drawn over the head from the nasion (centre of the naso-frontal suture) to 

 the inion (external occipital protuberance), a point 1 cm. (or half an inch) behind 

 the centre of this line will indicate with sufficient accuracy the spot where the 

 fissure of Koiando meets the upper border of the hemisphere, and may be termed 

 the superior Rolandic point. From 8 to 10 cm. farther back the lambda may be 

 felt, or if that is not possible, a point should be taken on the nasio-inial line 6'5 cm. 

 (or 2| inches) above the inion, and a line carried transversely outwards for a 

 distance of 2 cm. from this spot will mark the parieto-occipital fissure. 



On the side of the head, a line from the lowest point of the infraorbital margin 

 to the centre of the aperture of the ear (Eeid's base-line) is taken as the horizontal. 

 This line is about parallel with the upper border of the zygomatic arch ; and 

 vertical lines are perpendicular to it. A spot on the base-line in the hollow between 

 the tragus of the ear and the condyle of the lower jaw is known as the preauricular 

 point. From the fronto-malar junction (p. 1) let a line be carried horizontally 



