"34 



HUMAN ANATOMY. 



.and rounded, as it lies within the middle fossa, but traced backward it passes 

 insensibly into the tcntorial area, supported by the tentorium cerebelli. This area 

 is concave from before backward and directed inward as well as downward, in 

 correspondence with the characteristic curvature of the tent-like dural septum. 



The borders separating the surfaces of the hemisphere are the dorso-mesial, 

 the infero-lateral and the infero-mesial. The dorso-mesial border intervenes 

 between the mesial and lateral surfaces and, therefore, follows the arched contour of 

 the hemisphere beneath the vaulted calvaria. The infero-lateral border, between 

 the lateral and inferior surfaces, is better defined in front, where it separates the orbi- 

 tal area from the external surface as the arched superciliary border (Cunningham), 

 than behind, where it is so rounded off as to scarcely be recognizable as a distinct 

 margin. The infero-mesial border intervenes between the mesial and the inferior 

 surface of the hemisphere. It is well marked in front, where it limits the orbital area 

 mesially, and again behind, where it corresponds to the line of juncture between 



FIG. 980. 



Lateral aspect of left cerebral hemisphere; dorso-median surface is somewhat foreshortened ; red lines indicate 

 boundaries separating parietal, teniporal and occipital lobes ; r, Rolandic fissure ; j. g .. i. g., its superior and inferior 

 genu; S' t S*, S 3 , S* asc., vertical, horizontal, posterior and ascending limbs of Sylvian fissure; /. p. c., s. p. c., 

 inferior and superior precentral; s/., if., superior and inferior frontal ; p. m., param'edian ; /./., mid-frontal ; </., 

 diagonal, here continuous with inferior precentral; />, />-, f> 3 , />', inferior, superior, horizontal and occipital limbs 

 of inter-parietal ; p. o., parieto-occipital ; /', f 1 asc., superior temporal and its upturned limb; f-, f- asc., middle 

 temporal and its upturned limb;/, o., transverse occipital; /. o., lateral occipital; A., arm centre; .5. T. O.,pars 

 basahs, tnangularis and orbitalis ; Arc. p.-o., arcus parieto-occipitalis. 



the falx cerebri and the tentorium and marks the division between the mesial surface 

 and the tentorial area. This margin has been designated the infernal occipital border 

 by Cunningham. 



The extreme anterior end of the cerebral hemisphere is known as the frontal 

 pole (pohis frontalis), and the most projecting part of the posterior end as the 

 occipital pole ( polus occipitalis), while the tip of the subdivision of the hemisphere 

 which projects below the Sylvian fissure constitutes the temporal pole (polus tem- 

 I'oialis). A short distance behind the latter, the inferior surface exhibits a well 

 ^\\\\v<\ pctrosal depression (impressio petrosa >; this is caused by the elevation cross- 

 ing the petrous portion of the temporal bone which corresponds to the position of 

 the superior semicircular canal. Under favorable conditions of hardening, tin- infero- 

 inesial aspect of the occipital pole sometimes displays a broad shallow groove which 

 marks the commencement of the lateral sinus. The groove is usually better marked 

 on the right side than on the left, in accordance with the larger size of the ri^ht 

 sinus as commonly found ; occasionally these relations are reversed, and frequently 

 n<> groove is n ( ..-ni/able on the side of the smaller sinus. In brains hardened in 

 situ, the gently arching curve of the hind-half of the infero-lateral border of the hemi- 

 sphere is interrupted I,\ a more or less evident indentation, the preoccipital 

 notch i incisiua prauiccipiialis >, at a point about 3.75 cm. (l^ in.) in front of the 

 occipital p.>le i Fig. 980). This notch, prominent in the child but later variable in 



