INTERNAL STRUCTURE 01- THE BRAIN STEM 1039 



iz(.'(l adiustnu'iits. In contrast to it, tlu- more recent inanimalian ac(|iiisition 

 ol ncoknicsis, ])y adding tlic acKantaiics ol rcllcction and deliberation, 

 makes motor reaction more llexihle aiul hehaxior more \\idel\ ada])tal)ie. 

 Tile ])eiiod ol rellc'ction and latenc\ permits ol ht't ter uiiidanct' of mo\-ement 

 b\' tlu' diri'ction ol \ ision, ol hearing' and ol ])ro])rioce]5ti\ f organization. It 

 likewisi' allords all ol those opportunities essential to e\teiisi\e teachal)ilit\'. 

 Extent to Which M \\im als Utilized Theik New Possession oe 

 Neokinesis. Although the mammals Irom their beginnings came into pos- 

 session of this great acKantage owr tlu' more lowly organized \ crtebrates, 

 they tlid not m all instances utilize it to its full extt'iit. Nor did it become a 

 sine (jua no)} guaranteeing a lull and tllectn i- di'xclopment of its potentialities 

 in all cases. Indeed, it setans much more as though tlu' mammals were contin- 

 ually strixing to lind that ])ath which might prolit tlu'in most in the de\elo])- 

 ment ol their new possession. But lor all their ellorts, the\ \\ ere surj^risingly 

 unsiiccesslul m arriving at the desired goal. I low they began to push forward 

 along this liiu' m their early nionotreme beginnings, how far short lhe\ fell 

 of an\ ri'al ]:)rogre.ssivc achie\ement, how ihey tried again and again, now in 

 marsupial specialization, now as rodents, insect noiws, bats, ungulates, 

 cetaceans or carnivores, but always without approaching nearer to the 

 desired tnd, is revealed by their several histories. That the\ had made 

 delimte contributions over and abo\X' the lower forms of \ crtebratt's in the 

 organization of motion and in the development of beha\ ior is not dillicult 

 to establish, "^'ct each ordinal specialization, with all its stri\ing in this 

 direction, seemed clelicu'iit m some essential ecjuipment whereb\' it might 

 fulfil the promise discernil)le in tlu- new accession to their development. 

 1 heir motor at 1 1 list men ts \\c'r(.; largely adaj.)ted lor trail sport at ion, for carrying 

 the body o\er the siirlace ol the earth, under the tarth, m the water or 

 through the air. These animals progressed but little in their constructive 

 processes as applied to their environment. Tluy accepted the earth as 



