TARSIUS SPECTRUM 113 



motor pattern which necessitates simultaneous association of the ocuhir, 

 cervical and brachial musculature. It is not surprising in this hght that the 

 inferior olive is poorly developed in tarsius and in marked contrast to the 

 proportions and conhguration of higher primates. 



The other features at this level serve to bear out the observations 

 ah-eady made concerning the motor and sensory organization, as these 

 functions are ilhistrated I^y the small size of the pyramid and mesial fillet. 



The great importance of the animal's automatic associated movements 

 is indicated by the size of its midbrain bundles, the posterior longitudinal 

 and predorsal fasciculi (PL.PD). The central gray matter has assumed its 

 position in the floor of the fourth ventricle, and above the central canal a 

 massive obex marks the point of ventricular transition. The nucleus of the 

 hypoglossal nerve has all the indecisiveness in boundary characteristic of 

 lower levels. Its emergent fibers are coarse and heavy. Lateral to this nucleus 

 is the dorsal vagal nucleus (Nvd). In the dorsolateral angle of the 

 central gray matter is the nucleus of the fasciculus solitarius (Nfs). 



The nuclei of Goll and Burdach (NG, NB) are both prominent and 

 partially invested by fibers forming their corresponding columns. The 

 nucleus of Burdach is remarkable in tarsius for the very high development 

 of the ancillary nucleus of Blumenau. The nucleus of Rolando (NR) 

 and the descending trigeminal tract (Trd) are further removed from the 

 periphery due to the moving of the dorsal spinocerebellar tract into a more 

 dorsal position. The reticular formation still occupies the largest portion of 

 the section and is characterized by its diffuse arrangement (Ref). In its 

 ventrolateral portion may be discerned the nucleus funiculus lateralis. 



LEVEL OF THE VESTIBULAR NUCLEI (fIG. 55) 



At the level of the vestibular nuclei the dorsal sensory field has changed 

 in character, as is the rule in all primates. It still represents proprioceptors, 



