TARSI us SPECTRUM 107 



than of its feet, legs and tail. In contrast with the lemur and marmoset, this 

 relation approaches nearer to the more highly developed anthropoids. The 

 explanation, however, depends probably not so much upon the high speciah'za- 

 tion in the upper extremities, as upon the low speciahzation in the lower 

 extremities. Tarsius uses the hind legs much as does a frog. It leaps from 

 branch to branch and hops upon the surface of the ground. The specializa- 

 tion of the legs is thus not particularly advanced for purposes of locomotion. 

 It is inferior to that in the forelimbs for such acts as the animal develops in 

 connection with procuring lood. 



The nucleus of Rolando (NR) is particularly prominent as a 

 sensory element. This is also true of the descending trigeminal tract 

 (Trd), from which it is obvious that the sensory innervation of the head 

 and face plays a conspicuous part in directing the animal's locomotion. The 

 head and face are especially provided with vibrissae about the chin, mouth, 

 and beneath the nose. Supraorbital vibrissae also exist. The central gray 

 matter (Cen) occupies a position in the center of the section but has 

 shown considerable migration dorsad, thus manifesting the general tendency 

 to assume its characteristic position in the floor of the fourth ventricle. 

 The ventral gray column has entirely disappeared, and its position is 

 occupied by a continuous irregular mass representing the formatio retic- 

 ularis grisea (Ref). Contiguous with the latter on its lateral aspect is 

 the intermediate medullary substance which contains the rubrospinal 

 (Rst), spinothalamic (Spt) and Dciterso-spinal (DT) tracts. 



On the periphery is the circumferential zone which contains the ventral 

 (Cow) and dorsal (Fie) spinocerebellar tracts. Immediately adjacent 

 to the ventromedial sulcus is a dense mass of decussating axons com- 

 posed of internal arcuate fibers arising in the nucleus oi Goll (NG). 

 These decussating fibers form the lower portion of the mesial iiilet (Mf). 



