SUMMAin 01 STRUCTURES 725 



SlMM AK'i' 



Wert' it possible to ^i\t' 111 sumniafv the- iX'latiNc xalucs ol tin- struftural 

 features eonsiclerecl in this eomparatiN i' re\ lew , the placi' ol Inst importance 

 would uiuloul)tecll\ lall to the pontile nuelei. Their testimony as prt'sentecl 

 in the j^reat anthropoids, eonelusi\ c-l\ demonstrates a progressiw (K'\tlop- 

 nu'iU indieati\e of expansions m lU'okmi'tie organization. I o the i'\ idenee ot 

 the pontile nuclei and the p\ramidal s\stem should be added that ol the 

 inferior olivar\ nucknis whose incrcasiniz; Nolume and |)rogrcssi\e gam m 

 delinition cU'notc lunctional incremt-nts m essential accessories to neokinctic 

 de\elopmeiit. Likew ist', the oculomotor decussation, indicating as it does the 

 degree of organization in ocular coiiiugation and binocular \ ision, adds its 

 increasing acKantages to the sum of those mlhu'iices which ck'\ I'lop m the 

 interests of lU'okinetic expansion. The indis[)ensable acti\ it\ ol \ isual control 

 for the acquisition and maintenanei' ol man\ skilli'd mo\ements, contributes 

 the benelits of stereoscopic xision to tlu' direction of liner manual manipu- 

 lations. And linall\, the dellorescence of the mesencephalic colliculi, pro- 

 gressively acKancing through the |)rimate order. t\ pifu-s that unmistakabl\- 

 evolutional process of telencephalization b\ which functions originallx' \ested 

 in lower segnu-nts ol the lU'uraxis gam more expansible represt'iitation in 

 those higher le\ els i-specialls pro\ided In t lu' cortical regions ol the cerebral 

 hemispheres. 



