TARSIUS SPECTRUM 105 



The dorsal field consists of a small column of GoII (CG),a large column of 

 Burdach (CB) and an extensive substantia gelatinosa (NR). Adjacent to the 

 latter is a wcll-dcfincd descending trigeminal tract (Trd). The separation of 

 the dorsal gray cohimn is less pronounced than in many of the higher forms. 

 The general proportions of the elements entering into this field suggest at once 

 a tail and lower extremity which give rise to a sensory influx much k^ss than 

 that from the hand and arm. It is probably the case that in tarsius differentia- 

 tion of the upper extremity is more effective than of the lower extremity. 

 The great speed and accuracy with which the hands are employed in the 

 capture of insects, and at the same time for prehensile purposes in ahghting 

 after its remarkable leaps, would seem to imply a specialization in the 

 upper extremity much superior to that in the hind limbs. 



The tail has no prehensile characteristics, and while it acts in a supple- 

 mentary manner for supporting the clinging posture of the animal, its activi- 

 ties indicate no great increment of sensory inllux. The size of the nucleus of 

 Rolando is indicative of facial innervation, which is essential to the animal 

 in guiding its locomotion. 



The lateral white column contains in its circumferential zone the spino- 

 cerebellar tracts (Fie, Gow) while in the intermediate zone are the rubro- 

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

 pyramidal status denotes a behavioral complex consisting of relatively few 

 components and extremely poor in its pattern for skilled acts. 



CAUDAL EXTREMITY OF THE DORSAL SENSORY NUCLEI (fIG. 52) 



Here the chief feature is the appearance of the three nuclear structures 

 representing discriminative sensory transmission from the body. The nucleus 

 of Goll (NG) is well defined but shows no evidence of the median unpaired 

 nucleus of Bischoff. This deficiency- in tarsius harmonizes with the fact 

 that the animal's tail is not highly specialized, although it acts in spring- 



