346 THE BRAIN OF THE TIGER SALAMANDER 



terminals of the descending and ascending fibers of the ventral funiculus, here unstained. 

 Nothing except the elements drawn is impregnated in this region. Presumably, the axons of 

 these cells enter the motor V root, the unimpregnated myelinated fibers of which are here 

 darkened by the Golgi fluid. 



Figures 41 to 44- — These semidiagrammatic sketches are made from horizontal Golgi sec- 

 tions of an advanced larva, with elective impregnation of the spinal lemniscus and a few other 

 details. X 30. The series contains 26 thick sections, numbered from ventral to dorsal. Sections 

 2, 3, and 4, illustrating innervation of the hypophysis, have been published ('42, figs. 56, 57, 

 58). Here sections 7, 10, 12, and 14 are drawn, with some additions in each case from inter- 

 vening sections. 



Fig. 41. — The section passes through the V and VHI roots, with impregnation of superficial 

 fascicles of descending fibers of both roots and ascending VHI fibers, some of which extend as 

 far as the cerebellum. No ascending sensory V fibers are impregnated. The loci of the III, IX, 

 and X roots farther dorsally are indicated by blood vessels which accompany these roots. The 

 thick arcuate fibers from the region of the calamus scriptorius enter a mixed tract marked 

 Im.sp., which here contains bulbo-spinal, spino-bulbar, spino-cerebellar, and spinal lemniscus 

 fibers. Most of the thin unmyelinated fibers here impregnated come from lower levels of the 

 spinal cord, and their further ascending course is shown in figures 42, 43, and 44. A few thick 

 fibers of the ventral funiculi are impregnated, some of which decussate in the ventral commis- 

 sure below the auricle. 



Fig. 42. — At this level, thick arcuate fibers in the vicinity of the first spinal roots descend in 

 the calamus region and after crossing join the spinal lemniscus. Some of these bifurcate with a 

 thick ascending branch and a slender descending. Farther forward under the auricle the 

 lemniscus fibers turn dorsalward in the ventral part of the isthmic neuropil, and here many of 

 them end. This is tr. bulbo-isthmialis of figures 38 and 39. The lemniscus fibers which continue 

 rostrad have collateral endings here. Other elective Golgi preparations from this lot show the 

 origin of spinal lemniscus fibers from the nuclei of the dorsal funiculus ('446). 



Fig. 43. — This section cuts the III nerve root and its nucleus and, in the isthmic neuropil, 

 dispersed fibers of the spinal lemniscus and ascending VIII root. Medially of these are axons 

 emerging from the gray of the trigeminal tegmentum, which turn forward and arborize within 

 the gray of the isthmic tegmentum (p. 185). 



Fig. 44. — At this level the few remaining impregnated fibers of the spinal lemniscus are 

 turning forward across the dorsal tegmentum to reach the dorsal thalamus. The crude drawing 

 gives a very inadequate picture of the delicacy of these widely branched terminal arboriza- 

 tions. The more numerous fibers of this tract, which arborize in the tectum, are not impreg- 

 nated in this preparation (compare fig. 101 and '396, fig. 26). For the patterns of vascular 

 supply sketched in the left thalamus see page 27. 



Figure Jf5. — Terminals of the dorsal lateral-line root of the facial nerve, from the right side 

 of a horizontal Golgi section of a late larva. X 50. Only three fibers of this root are impreg- 

 nated, and each of these ramifies through almost the entire extent of the "dorsal island" of 

 the area acusticolateralis immediately spinalward of the auricle, which is the exclusive central 

 field reached by fibers of this root (compare fig. 33). 



Figures ^6 and ^7. — Details from horizontal Golgi sections of an advanced larva. X 75. 



Fig. 46. — A neuron of the anterodorsal part of the trigeminal tegmentum in the ventral 

 part of the auricle (p. 185). The plane of section is approximately that of figure 31. 



Fig. 47. — A small neuron at the anteroventral border of the body of the cerebellum, where it 

 merges with the nucleus cerebelli. The slender dendrites extend outward into the dorsal part of 

 the isthmic neuropil, and the axon is directed forward and downward into the brachium con- 

 junctivum. Fibers of the trigeminal component of the cerebellar commissure (com.cb.) are 

 approaching their decussation immediately dorsally of this level, as also are more scattered 

 fibers of the vestibulo-lateral component (com.cb.L). 



Figure ^8. — Detail from a transverse Golgi section previously pictured ('42, fig. 43). X 50. 

 The small neuron of the dorsal tegmentum has a short axon, which ramifies in the deep 

 neuropil of the gray near the cell body and also dorsalward in the alba of the anterior end of 

 the nucleus posterior tecti. On the vascular loops {b.v.) seen here see page 27. 



