THE BRAIN OF PREHISTORIC MAN 8-i 



The Fissurk of Rolando. The lissurr of Rolando (sulcus cintralis) 

 nia\ in a i^cneral \\a\ \)v placfcl hctwcfn the two inani branches ol the middle 

 nu'iiiiimvd artciN and in front of the parietal eminence'. Estnnatcd l)\ the 

 anthropometric criteria of this lissinx' now <j;encrall\ accepted, the upper 

 extremitx of the lissm-c may be |)laced on or near tlu' superior lon<j;itudmal 

 groove about 2 cm. posterior to its niidpomt. calculated as one hall the 

 distanci' iVom the frontal to the occipital vm\ of this yroo\e. The <i;eneral 

 direction of the Rolandic fissure ma\ likewise be estimated as a descending 

 line which leaves the superior longitudinal groo\c at an angle ol inclination 

 forward of somewhere betwct'ii 6"'" and "1.4 . The allocation ol this most 

 important boundarx is lAtreiiu'ly generalized and must of necessity omit many 

 essential details of the sulcus. It allords no intimation as to the extent ol the 

 fissure, or tlu' relations of its upper and lower extremitU's to the superior 

 longitudinal fissure on the one hand and tlu' lissure ol S\l\ius on the other. 

 Neither does it denote the presence of the usual geiuillections conspicuous in 

 the human central sulcus. Idu- position and disposition ol the Rolandic 

 fissure assigned to the l)rain of pithecanthropus depend more upon deduction 

 and analog\- than actual indications on the cast. It is dcsirabh', howi'\er, to 

 establish certain approximations regarding the character and position of 

 this lissurc. 



Thi£ Gkoo\e of the Tka\s\'Erse Si.m s. The third landmark is the 

 groove of the transverse sinus which indicates the planes ol se])aration 

 between the occipital lobes of the cerebral hemispheres and the cerebellum. 

 This groove w ith the sui:)erior longitudinal furrow marks the position ol the 

 torcula hero|)hili. 



These boundary lines determine the general extent of four great lobes 

 in the brain, namel\, the frontal, parietal, temporal and occipital. It is 

 possible in the light of this topography to consider tiie characters and sig- 

 nilicancc ol each lobe separately. 



