STRUCTURAL CULMINATION 969 



should show the <ir(.';itcst degree of eomokitional nehness in man is 

 what might be expeetetl jii \ie\v ol Ins hi'tter powers oi reason and iudg- 

 ment. hrs greater abilit\' to proht 1)\' experienee and his more ample 

 eapaeitx' to eonstruet those eomplex neural s\iitheses in the eonslitution ol 

 liuman ])ersonality. 



B\' archious labor and ingenuit\, hieroglx phies ot several dead languages 

 ha\e been deeiphered and tluir geni'ne relations in linguistie de\elo])ment 

 established. It requires no sueh ellort to interjiret the signs inseribid upon 

 the neopallium ot the eerebral hemisplu-res in the primate order. ii-om the 

 sim]jlest hssural inseriptions, tlirough all degrees of elaboration in their 

 inereasing struetural eomplexity, tluir translation reveals a progressive 

 ex]:)ansion m the endbrain. Sueh also is the e\idenee deri\ed Irom tlu' loba- 

 tion ol the hemis]:)here with its inereasing eomplexity in eon\'oliition. 

 \\ itliout hiatus or ambiguit\ these faets ])ro\"ide a eomplete reeord of e\()lu- 

 tionary progress in the brain ol primates. 



E\OLUTiONAL Significance oi- ihe Basal Structures. On the base 

 of the cerebrum, in that portion whieh comes in contact with the orbital 

 plate ot the Irontal bone, the |)rocess of gradual unlolding is lurther illus- 

 trated. The orbital plate in the lower primates shows a convexity correspond- 

 ing 111 ])osition to the orbital socket which produces a conca\it> m tlu' orbital 

 surlace ol tlie brain. As tlie hemispheri' in its Irontal area beconu's more 

 expanded this conea\it\ decreases. In consequence the orbital concavity 

 IS most i^ronoiinccd m tlu' lower primatt's. It is a feature of consicU'rable 

 prominence m the intermediatt' primates, is conspicuous e\"en m thi' bi'ams 

 ol the orang and the chimpan/.ee, but shows its first marked decrease in 

 the gorilla. Although exidence ot it ma\ still be toiind in tlu' human brain, 

 It IS hert' so inconsiderable that it might tail to attract attention. Associated 

 with tin- orbital conea\it\' is another notal)le feature, the intcrorhilal kt'cl. 

 1 his mesial ridge is most prominent in those species with the deepest orbital 



