SLMMAin OF STRUCTURES 703 



COMPARISON OF THE PYRAMIDAL SYSTEM OF THE (iREAT ANTHROPOIDS AND 



THE LOWER PRIMATES 



Contrasted with tlir lowtr priinatcs, the acKancc ot the |)\raniiclal sys- 

 ti'in maiiite'stcd by thr <i:ii'at anthropoids puts tiu' qut'stion ol progressive 

 c'X]jaiisi()n in lU'okinctic function entu'rly Ix-yond the rcahn ot doubt. No more 

 striking instance of e\'ohitional progress may be found tlian that represented 

 by the remarkable disparity in pyramidal development between the lower 

 primates and the higher anthro|)oids. In only one instance, namel\ , mycetcs, 

 does the pyramidal coellicient e\en approximate that of tiie great apes. 

 The lemur and the marmoset are so far distant from the chimijanzec, gorilla 

 and orang in this department of their organization as almost to seem repre- 

 sentatives of another order. From this lower limit to the higher one, a steady 

 expansion in neokinesis appears to have exerted an irresistible inlliience in 

 progressively expanding the sphere ol bt'havioral reaction. 



n. The Oli\arv Nucleus in Relation to the Regi lation oi- Simul- 

 taneous Movements in the Eves, Head and Hand and the 

 Facilitation of All Skilled Learned Performances 



The relation of the inferior oli\-ary body to the control of simultaneous 

 movements of eye, head and hand and to the tacilitation ol coordination of 

 all skilled learned performances, ascribed to this structure in this discussion, 

 should be accepted with certain rcserxations. In any case, the structural 

 evolution manifested by the nl'wv within the famil\ limits of the Simiidae 

 is bcNond dispute. The gorilla presents an inlenor olixarv body which is 

 considerabU' larger in its planimetric coeHicient than that ot either the chim- 

 panzee or the orang-outang. Combined w ith this adxantage in size accredited 

 to the gorilla, other structural filatures indicate a further specialization in the 

 olive. The degree of convolution and the dellnition of outline attained by the 

 olivary body are features of utmost importance in determining the difleren- 

 tiation of this structure. In this respect the gorilla approaches most closely 



