SUMMARY' OF STRUCTURES 711 



conipai'c'cl with thr Idi (.'limhs In ilu' ^nvit antliropnicls this disparity is so 

 marked that tin- culuniii dI (h)II is less than hall Of the si/.c of the adjacent 

 column ol Burdach. Such disproportion in laxorol Burdach's column ma\' 

 be accepted as \alid e\ ideiice. Its gradations ma\ he traced throu<i;h inter- 

 mediate stapes Irom a condition in which the column ol Burdach is dis- 

 tinctly less than that ol Goll in tin- lower primates, to one in w hich it is much 

 greater, as m the hi<j;her sjjccics. It is |)ossil)le that nuclear structures such as 

 those ol Coll and Burdach st'r\ iiiu as primarx relaxing stations for sensory 

 afierents, may, without \ar\ing nuich m size them.seKes, ofliciate in this 

 capacity e\en when the sensory tracts associated with them become much 

 increased in xolume. 



This discussion may appear to absoKf the dorsal nuclei by oliering 

 certain extenuations lor their apparent lailure to rellcct the ellects ol adap- 

 tive ciianges in the extremities. It should m no wise depreciate the evidence 

 aOorded l)\ the dorsal sensory held itsell. The lact that there is a j)ro<iressive 

 increment in the- mllux ol sc'iisor\- impulses Irom xUv upper extremit\', as 

 compared with the lower extremity m ascendin<i the primate series, remains 

 unassailed. \\hate\cr may be the relative size ol the primary relaying 

 nuclei of thi-se special seiisor\- systems, tiie conduction paths leading to them 

 Irom the jjropriocejjtors disclose a relatne \'olumetric change m conduction 

 capacity. The ratio of the column of Burdach to the column of Coll in lemur 

 is one to one and a hall. This ratio in the gorilla and all ol the other greater 

 anthropoids is two to one. It is dillicult to mterj^retthis increase m the volume 

 of sensory mllux on grounds other than the specialization ol the ujjper extrem- 

 ity and particularly of the hand. Signilicant also is the relati\e decrease 

 in the sensory inllux from the head and face as indicated by the substantia 

 gelatmosa trigeinini in its relation to the nuclei ol Coll and Burdach. It is 

 apparent from this interrelation that imicii sensor\- responsibility has i^ecn 

 delegated from the primiti\ (.ly imjjortant areas of the head and face m their 



