7o6 THE HIGHER ANTHROPOIDS 



forms is so decisive as to justil\ the supposition oi an evolutionan progress 

 in tlu' physiological function ot the inferior oh\ar\ body. 



111. The Dorsal Sensory Nuclei in Their Relation to 



DiSCRlMINATn E SeNSIBILITY IN THE EXTREMITIES 

 THE NUCLEUS OF COLL 



The nucleus ot Goll ui the three great apes diflers in its function from 

 that of the lower and intermediate forms in the fact that the great anthropoids 

 do not develop a tail. Hence an important sensory area of the body has 

 ceased to exist. The absence of this organ should appreciably impress itself 

 upon the development of the sensory elements in the neuraxis designed to 

 receive the aOerent inllux from the proprioceptors. As amongthegreat anthro- 

 poids themselves, the gorilla has developed the nucleus of Goll to a greater 

 extent than either the chimpanzee or the orang. This may in part be due to 

 the slight advantage which tht' greatest of these primates has in the develop- 

 ment of Its foot, which is somewhat better adapted to plantigrade locomotion 

 than that ol either the chimpanzee or orang-outang. This interpretation 

 is based upon facts already determined concerning the structural features 

 of the gorilla foot as compared \\ith his anthropoid associates. It also takes 

 into account the supposition that the gorilla, because of his great weight, is 

 iorct'd to go much more upon the ground than the smaller, more agile 

 members of his family. This position, however, may not be accej)ted without 

 some reser\atioiis. That locomotion upon the ground has some bearing upon 

 the expansion of the sensory areas, more particularl\ the tt'iidcncx to assume 

 the upright posturi', is a \i(.'w \\ huh gams some substantiation from the 

 know n bt'ha\ ioral reactions ol the Simudae. The |)lani metric and longitudinal 

 coefficients of the nucleus of (joII, gi\en in the follow ing tabulation, show a 

 fairly distinct acKantage in the de\ I'lopment ol this structure in the gorilla 

 over tin- other two forms: 



