348 



THE BRAIN OF THE TIGER SALAMANDER 



Figure 49. — A typical neuron of the dorsal tegmentum from a horizontal Golgi section of 

 an advanced larva. X 75. The ependymal surface is marked by a thin line at the left, the pial 

 surface by a thicker line at the right, and the outer border of the gray by a broken line. The 

 axon arises from the dendrite and is directed spinalward (downward in the figure) and prob- 

 ably enters tegmental fascicle (7). A similar neuron >Ji s-itu is shown in figure 44 of the 

 paper of 1942. 



Figure 50. — Horizontal section through the decussation and spiral endings of the f. retro- 

 flexus (p. 197). Golgi method. X 50. The semidiagrammatic drawing is based on several adult 

 specimens, in each of which the fasciculus of both sides is massively impregnated from the 

 habenula to the interpedvuicular neuropil. All details drawn are visible in two sections of the 

 specimen outlined (no. 2229), wliich is, however, poorly preserved. Several otlier series of sec- 



tions show the same relations more clearly, though the oblique planes of some of the sections are 

 less convenient. The considerable lateral obliquity of one of these gives an interesting view of 

 the interior of the spiral. In these specimens the spiral endings are impregnated for about two- 

 thirds of the distance between the decussation and the level of the V'roots. 



Figures 51 and 52. — Two adjoining horizontal Golgi sections of a late larva, illustrating the 

 decussation and spiral terminals of the f . retroflexus, which is impregnated on only one side. 

 The right side is more ventral. X 50. 



Figures 53 and 54. — Two adjacent thick horizontal Golgi sections from an advanced larva. 

 X 50. 



Fig. 53. — At the level of the fovea isthmi (f.i.) and the decussation of the f. retroflexus. 

 Laterally of the interpeduncular neuropil are impregnated fibers of tr. olfacto-peduncularis, 

 with endings by open arborizations in this neuropil; compare figure 59, cut in a similar plane a 

 little more dorsally. 



Fig. 54. — Ventrally and posteriorly of the decussation only a few isolated fibers of f. retro- 

 flexus are impregnated, and tr. olfacto-peduncularis is terminating in the ventral inter- 

 peduncular neuropil in the same area as the spiral. The tufted endings seen here are not derived 

 from either of these tracts. 



