354 



THE BRAIN OF THE TIGER SALAMANDER 



laris. A few neurons of the interpeduncular nucleus are incompletely stained, but apparently 

 no axons from these cells are impregnated. The dense interpeduncular neuropil here seen is com- 

 posed almost exclusively of axons from the tegmentum and tr. mamillo-interpeduncularis. 

 Terminals of the latter, when separately impregnated, are seen to be of more open texture than 

 the dense vertically arranged terminal tufts of the tegmento-interpeduncular fibers (fig. 60). 

 The two types of terminals are closely interwoven with each other and with tufted terminals 

 derived from axons of neurons of the interpeduncular nucleus (not here impregnated) . 



f.lat.t 



tr.teq.b 



Fig. 60. — This section lies between the nuclei of the III and IV nerves, i.e., between the 

 levels of figures 92 and 93, at about the level of figure 13 of 1936 and two sections rostrally of 

 figure 39 of 1927. The drawing is a composite, containing some details from the two adjoining 

 sections. Axons from both dorsal and isthmic tegmentum descend in the f. tegmentalis pro- 

 fundus, some terminating in the underlying interpeduncular neuropil and some of thicker cali- 

 ber decussating in the ventral commissure (fr.ieg.b.), where collaterals separate from them to 

 end in tufts of the interpeduncular neuropil. In figure 39 of 1927 these decussating fibers are 

 called tr. tegmento-peduncularis, and the same fibers are here called tr. tegmento-bulbaris. 

 Both designations are correct. The larger number of these fibers after decussation turn spinal- 

 ward, some sending collaterals forward also. Others turn rostrad into the peduncle. 



Fig. 61.— This section passes through the nucleus of the IV nerve, and the three neurons 

 impregnated probably belong to this nucleus. Approximately the same plane is illustrated in 

 several published figures ('25, figs. 9, 19; '36, fig. 14; '42, fig. 43). At this level the myelinated 



