SUMMARY OF STRUCTURES 



259 



hand in acts of discrimination and selection. The planimctric coefficient of 

 the nucleus of Burdach in mycetes is sHghtly in excess ot that of any of the 

 other primates including the anthropoids and man. This observation will be 

 more fully discussed in connection with humanoid and human manual ditler- 

 entiation. In general, it seems to indicate a strong adaptive iniluence operat- 

 ing in direct response to the specialization of the prehensile tail which has 

 largely freed the forelimbs from functions of locomotion. It has thus made 

 them available for more complex motor patterns utilized in exploring and 

 further dominating the environment. The tabulation of coefficients follows: 



Planimetric Coefficients of Dorsal Sensory Nuclei in Lower Primates 



Advances in the nucleus of Goll and more especially in the median 

 nucleus of Bischoff are measurably demonstrable in mycetes as an apparent 

 response to the adaptive modifications incident to the development of the 

 prehensile tail. This species, compared with lemur, tarsier and marmoset, 

 shows a similar advance in the nucleus of Burdach as a consequence of 

 further manual diiferentiation. 



