RECONSTRUCTION OF TROGLODYTES NIGER 617 



in the upper If\els ol the iiU'scnccphaloii the reticular formation is to a 

 great extent rephieed m its \entral portion l)\ the nucleus ruber. Dorsal to 

 the nucli'us ruber, ho\ve\er, a portion ol the lorniatioii remains and continues 

 upward to merge with the reticular lormation ol the dieiicephalcMi. 



The PoNiiLE Nuclei 



The ])ontik' nuclei j^resent an exceedingly c()mj)licaled appearance. They 

 begin below as thearcilorm nuclei which first appear at about the mid-olivary 

 level. The arcilorm nu(.k'i lorm a relati\el\ simple la\er of gray matter sur- 

 rounding the p\ramid. This jjyramidal iiuestment creeps further laterad 

 until the nuclear material extends completel\' around the pyramidal tract. 

 The amount ol nuclear material increases, i^rcsenting an extreme com|)lexity 

 in its deveiopmeiit. It still maintains, howexer, the primitive arrangenu'iit of 

 a \entral or superhcial layer and a deep or dorsal layer. These two are con- 

 nected at their extremities by means ol the two buttresses at the mesial and 

 lateral aspects ol the nuck'ar lormation. 



The supcrlicial la\fr corri'sponds closel\ with the surlace ol the pons, 

 expanding into the lateral buttri'ss and coming into close contact with the 

 ventrolateral angle of the reticular lormation. Tlu' mesial buttress is an 

 extensive mass ol gray mattt-r lying in contact with its tellow of the opposite 

 side and lusing dorsall\ w ith the deep la\i'r ol the pontile nuclei. The union 

 ol the two nuclear massi's across tlu' mKllme is so extensive as to lorin a 

 shield-like structure, o\crlapped on either sick- by the ventral prolongation 

 of the superficial layers ol the pontile nuclei. The internal, lace-like arrange- 

 ment ol the nuclei is prominent in the chimpan/.ct'. MassiNc strands of 

 nuclear mattrial ])ass trans\ frsely between tlu' two buttresses and j^resent 

 branch-like forms which pass to the lateral and mesial buttresses. These 

 strands of gray matter serve to break up the pallio-spinal and pallio-pontile 

 tracts into a great number of smaller bundles. The pontile nuclei are continued 



