730 



THE NERVOUS SYSTEM 



infero-lateral border of the hemisphere, the hue in question aviII nidieate the adja- 

 cent margins of the parietal, temporal, and occipital lobes of the brain. 



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'cerebrum 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 convolutions and the 



sulci which separate them. , . , ^ . . , ^ ^ i ,• 



In every consideration of the topographical relations of the cerebral convokitions 

 to the walls of the cranial cavity it must be borne in mind that the conditions are 



Fig. 434.— Drawixg of a Cast of the Head of a Newly-born Male Infant. 

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



EXTERNAL 

 PARIETO- 

 OCCIPITAL 

 FISSURE 



FISSURE OF 

 ROLANDO 



POSITION OF PARIETAL 



EMINENCE 

 POSITION OF FRONTAL 



EMINENCE 



FISSURE OF 



SYLVIUS 



PARALLEL 



FISSURE 



not constant, and that, therefore, the relations are variable. The three main factors 

 upon which this varial)ility depends are age, sex, and the shape of the skull. As 

 examples of the variations which occur it maybe mentioned that the fissure of 

 Sylvius is higher in the child than in the adult (compare figs. 433 and 434). The 

 upper end of the fissure of Rolando is further away from the coronal suture in 

 the female and the child than in the adult male, and in dolichocephalic than in 

 brachycephalic heads. The angle formed betAveen the line of the fissure of Rolando 

 and the mid-sagittal plane, which averages about 69° in the adult, is niore acute 

 in dolichocephalic heads, and the external parieto- occipital fissure is further 

 forwards in the cliild, and possibly in the female, than it is in the adult male. 



