1028 EVOLUTIONAL MODIFICATIONS 



developmental gradations until it attains its definitely convoluted stage first 

 seen in the gibbon, but steadil\ inereasing its nuclear indi\iduality in the 

 higher anthropoids and num. Not alone does this nucleus acquire decisive 



COMPARATIVE PLANIMETRIC GRAPHS 

 c. Cerebral Peduncle 



FIG. 539. GRAPH BASED OX PLANIMETRIC INDICES OF CEREBRAL PEDUNCLE. 



This structure is of particular significance in neokinetic evolution. It is a concentrated expression ot the 

 neokinetic powers of the cerebral cortex, representing as it docs the palliospinal and palliopontile projection 

 systems. Functionally it provides for the conduction of impulses essential to volitional and coordinated 

 control of the muscles. It is of an exclusively mammalian character in the brain, showing its greatest expan- 

 sion under the influence of arboreal life and the consequent development of quadrumanous specialization. 



