,04 THE HIGHER ANTHROPOIDS 



largt'h faxors the column of Biirdach clearly indicates what considerable 

 gain the upper e.\treniit\ has made as a chscriniinati\ e and locomotor organ, 

 and thus illustrates the reflection of that process w hich has as its ultimate 

 goal the most complete dilVerentiation of the upjjcr extremity ada])ted 

 to the purposes of neokinesis. The hand and ttie arm ol the orang have 

 not attained that degree of adaptability which is seen in either ot tlie two 

 other great anthropoids, the chimpanzee and the gorilla. On the other 

 hand, as an organ for exploring the einironment and lor the prodiiction ol 

 man\- more complex and learnt'd perlormances, the lorelimb ol the orang 

 has made decisive advances over that ot the gibbon or an\ ol the inter- 

 mediate primates. 



LEVEL OF JCALDAL E,\^HU.Mn^ Ol DORSAL SENSORY NUCLEI (FIG. 230) 



At this U'\cl the most important modilications haxe occurrt'cl m the 

 dorsal fields where a detached nuclear mass near the dorsomedian septum 

 has made its api)earanee. This is the nucleus of Coll ( NG) which is invested 

 by a dense mass ol m\elini/ed ner\e libers, the column ot Goll ( CG ). The 

 boundai'N liiu- betwi'cn this column and that ol the column of Burdach 

 (CB) is indicated by the |:)resence ol a poorly detined dorsal paramedian 

 sulcus, while tin latt'ral boundarx of Burdach's column is nearix li\e times 

 that of Goll. This coincides with the spi'cializ.ation going forward in the 

 upper extremitx of the animal, particularl\ the de\elopment of xhv hand and 

 the long powerful forearm, while tlu' absence ol the tail and the relati\el\ 

 low degree of dexelopment in the short legs account lor a dillerence m 

 which the column of Goll appears to i)e the smaller of the two. No detached 

 nuclear mass is seen as yet m the column of Burdach. Near the base ol the 

 central gray matter (Cen) a small dorsal protrusion marks tlu' beginning 

 of the caudal extremity of the nucleus of Burdach. Tlu'se two nuclei in the 

 dorsal column present, throughout the entire series ol primates, a contrast- 



