STRLCTLRAL CULMINATION 983 



ture was a critical one. By ■ - accepts rees as their lot, and 



man, because of his tAvo they supp>orted above them, 



acquired the earth with all it contained. Thus, with arboreal life a thing of 

 the past, with a true ground-gripping foot ^ntigrade bip>edal locomo- 



tion, with longer legs and actual erectness for cdectiAe transportation, the 

 hands were finally liberated for - . success. 



The specialization o: -.e been in process 



through great period- " . .<s the decisive parting of the ways be- 



tween the apes and the i. :y. For however permissib vbeto 



regard the upper extren .itferentiation, as the 



most cogent influence affecting the exp., - t the b er, 



the hand itself was ultimately depe ierentiation ot human 



feet. Nor is rt p>ossible to omit all of those factors in structural organization 

 which finally made possible the erect . setting the heac the 



shoulders so that the eyes might look : the hands 



follow the direction of the eyes. 



Upon the dorsal si;: rain stem, the record of progressive 



expansion may also be discerned. A om the conspicuous evolutional 



features in the cerebellum, ex-pressed especi. :he pronounced expansion 



of the lateral lobe, this region of the brain contains other elements equally 

 significant, if less conspicuous. TTie progressive increments in the clava and 

 cuneus, those structures -orsal sensor\- field representing the sensory 



influx from the upp>er and lower extremities, have already been discussed 

 in their functional aspects. That both of them should enlarge in passing 

 from the lower primates. _-h the intermediate group, to man, has its 



explanation in the augmented stream of afi^erent sensor].- impulses from the 

 deep proprioceptive structures of the btxly. Fluctuations in the interrela- 

 tions between the clava and the cuneus are of even greater moment. In 

 the lower primates it is the clava \\ hich shows more prominence. Recerving 



