INTERNAL STRUCTURF OF THF I^I^MN STFM 1007 



vast siipcrstriicturi' representing the ei\ilize(l world with all its rich 

 content created by the industries and ellorts of man. Delined in a single 

 term, this new sphere of action has been called ucoliinesis. Its motor possi- 

 bilities were first revealed by the ad\ent of mammalian forms. They marked 

 the beginning of that long ])eriod of" cNolutionai progress which constantly 

 kept in the foreground the de\ elopnuntal potentiality- offering the greatest 

 ultimate promise. Simple as is the neokinetic specialization in most of the 

 lower mammals, it may nevertheless be discerned in its incipiency at that 

 stage of organization w hiii llu' cerebral cortex first began to differentiate 

 a motor zone for voluntar\ control o\er the muscles. This motor zone of the 

 cortex acquired connections with the lower st'gnu'nts of the axis through the 

 projection libers of the jnramidal system, which introduced all of those 

 advantages accruing from ])rogressi\e expansions in the hemisphere. 



Neokinesis and Dexelopmem 01 Mil llwn. A sur\e\ of mammals 

 clearly indicates that those orders wlmh ha\c manifested the greatest 

 capacity in de\cl()])ing neokinesis gradually tended to acc[uire ascendancy. 

 Certain orders among thi- mammals, not distinguished b\ their neokinetic 

 development, have passed into habitat zones in which tlu\ rexcal no con- 

 structive prei'mineiice. They have attained only that scant margin of suc- 

 cess which secured to them a nominal degree of permanenc\ in their organic 

 differentiation, flow true this is may be set'ii in the history of the carnixores 

 and ungulates, rodents and insectivores, marsupials and monotremes. 

 EcjuallN true is it of the pinniped mammals, which bv secondary adaptation 

 have readjusted their somatic and \ iseeral organization to aquatic lilV-. But 

 the branch of the mammalian stem which manifested a real tendency toward 

 manual ditienntiation furnishes a totally diflerent record in the history 

 of neokinetic expansion. The fust impulses toward this manual differentia- 

 tion developed certain morphological extremes as, for example, c[uadru- 

 manal specialization, and thus committt'd the animal to a t\pe of habitat 



