STRUCTURAL CULMINATION 963 



loht' IS rmu'li mori' piDmiiU'iit l\ lissuri'tl than in cithrr ol x\\c two uix'at ant hro- 

 |)()i(ls assoc'uilc'd with it. The lissurt' ol S\ Kins tends to l)c' more liorizontal 

 in Its (lirc'c't ion, while 1 he lissure ol l-\olanclo departs Ironi the superior longi- 

 tudinal lissnre with an aiif^iilar iiulinat ion of something less than ~j degrees. 

 I he marked ehanges in the lissiiral pattern of tlie great anthropoids therefore 

 consists in the eonvolutional riehness seen both in the Irontal and oeei[)ital 

 lobes, with the presence ot excry lissnre lound in the iuiman brain more 

 prominentl\ marked than in the intermediate primates, and with marked 

 accessions in the Innital and occipital regicjns incident to expansion in these 

 |)ort ions of the brain. 



In man the lissural pattern attains its greatest complexitx, so nuieh so 

 that It bieomes dillienh to identil\ the se\eral eharaeteristie fissures, which 

 in the lowt'r primate brain stand out in prominence because of tlu' relati\c 

 sim])licit\ in the siileal markings. The lissure ol Rolando now has an angle 

 ol inclination with the superior longitudinal lissure of about ~i degrees; the 

 lissure ol SyKius apjjroaches much nearer to the horizontal than in any olthe 

 lower species; the sulcus simiarum has jjiactically disappeared and nothing 

 suggestixe ol it is to be seen in the human brain unless it be the sulcus lunatus 

 referred to by Elliot Smith as tlu' possible homologue of the sulcus simiarum. 

 The general position ol this lissure is marked by the parietal incisure ol the 

 occipito-parietal sulcus. The occi|.)ital lobe itself shows a richness of lissures 

 generally arranged aljout the occipital and lati'ial occipital sulci, which far 

 exceeds in compIe.\it\ an\ thing obser\ed in the primates Ik'Iow man. 



The evidence, therefore, oHered by the lissural pattern in the primate 

 brain, especially as it alfects the lateral surface of the hemispheres, points 

 to a progressive evolution, starting with a pattern in many respects reminis- 

 cent of the carnivore circumsylvian type, and passing from an almost indif- 

 lerent intermediate stage of the simplest lissenccphalic neopallium, through 



