INTERNAL STRUCTURE 01- THE BRAIN STEM 1037 

 Plankmetric Coefficients of the Pkimaie Bi<\i\ 



SUMMARY' OF THE E\ IDEXCE OF AN E\'OLl'TIONAL PROCESS AFFORDED BY THE 

 E.XTERNAL AND IMER.XAL APPEARANCE OF THE PRIMATE BRAIN 



In sum total, the evidence atlorded In the external appearance of the 

 brain m [jrnnatcs, and l)\ its nitcrnal structure, points conclusu cly to an 

 c\'<)lutioiial process which has run paralk-l with corresponding expansions in 

 behaxioral de\ elopnunt. Thi.s exohitional process, both in structure and la 

 function, has made itself apparent most particularl\ in tlu' accessions to the 

 sphere of neokinesis, which new t\ pe ol' motor expression has been the distin- 

 guishin<i contribution of the mammals. It was, in this respect, as though 

 their arri\al had at once opened a lU'w trail which led into realms of more 

 highly speciali/.ed bchaxioral d(.\ tlopment. 



Neokinesis and P\i iokinesis. This new motor specialization intro- 

 duced b\ tlu' mammals had certain acKantages oxer the ancient type 



