326 



C. JUDSON HERKICK 



compost. 



TrT.Th.h, 





trT.th,h.c.p. 



Fig. 3S Three sections farther ventrallj-, including the habenula, pars in- 

 tercalaris diencephali, commissura posterior, and the rostral end of the tectum 

 mesencephali. The tractup tecto-habenularis (tr.t.hab.) shows free endings 

 within the habenula. Fibers of the tractus thalamo-Deduncularis dorsalis 

 superficialis (tr.th.p.d.s.) are seen arising from the pars intercalaris diencephali, 

 and some of these fibers seem to arise farther forward in the habenula. X 30 

 (cviic, 7). 



Fig. 39 Thrpe sections farther ventrally through the subcommissural organ 

 (o.sc.) and the ventral part of the habenula {hah.) and pars intercalaris dien- 

 cephali (pA.ih.). The slender neuron in the rostral part of the pars intercalaris 

 on the right side is drawn in from the adjacent section dorsally. Its axon is 

 directed toward the tractus thalamo-peduncularis dorsalis superficialis. Many 

 similar neurons are impregnated, one imperfectly on the left side of this section. 

 Their dendrites spread among the fibers of the tractus tecto-thalamicus rectus 

 and tractus spino-thalamicus. On the left side is seen the connection of a 

 slender wisp of fibers of the tractus thalamo-peduncularis dorsalis superficialis 

 (tr.th.p.d.s.) with the caudo-ventral part of the habenula. See figure 41 for 

 the further course of these fibers. On the left side is a superficial area of neu- 

 ropil laterally of the superior commissure, which is composed of peculiar ver}^ 

 fine and freely branched varicose fibers. They are apparently terminal arbori- 

 zations of axons of unknown origin. There are some indications that these are 

 short axons arising from the cells of the stratum griseum of the pars intercalaris 



