ILLUSTRATIONS 



337 



alba. The same fibers after decussation appear in the superficial tract, A, and in the deeper 

 fascicles of group (8). Rostrally of the V roots, most of the thick fibers of the ventral com- 

 missure belong to tr. tegmento-bulbaris cruciatus. Among these the f. longitudinalis medialis 

 is assembling from fascicles of groups (4), (5), and (6) (p. 281). Medially and dorsally of these 

 are finer fibers of the dorsal division of tr. interpedunculo-bulbaris (tr.inp.b.d.). 



Fig. 28. — Through the hippocampal commissure and the middle of the sensory root of the 

 V nerve. The section cuts the ramus communicans posterior of "the arterial system (r.c.p.) 

 and the decussation of the posterior division of tr. tecto-bulbaris cruciatus {tr.t.h.c.2.), also 

 the most ventral fibers of the commissure of the tuberculum posterius. 



AA-I2S 



Fig. 29.— This passes immediately below the cerebral flexure at the tuberculum posterius 

 and the ventral border of the peduncle. Mingled with the crossing fibers of tr.f.b.c.2. are the 

 most ventral crossing fibers (unmarked) of the anterior division of tr. tecto-bulbaris cruciatus. 

 The central nucleus of the isthmus (nuc.i.s'.c.) is here well defined, and laterally of it are ter- 

 minals of the dorsal tegmental fascicles of groups (7) to (10). 



Fig. 30. — This section cuts the ventral border of the junction of the peduncle with the isth- 

 mus, a locus marked by the superficial origin of the III nerve. The anterior division of tr. 

 tecto-bulbaris cruciatus (tr.t.b.c.l.) is decussating within the ventral tegmental fascicles of 

 group (1) (p. 277). More posteriorly, the section cuts the dorsal border of the sensory V root 

 and the visceral sensory roots of the VII and IX nerves, showing the entire prevagal part of 

 the f. solitarius (pp. 148, 166 and figs. 37, 38). 



Fig. 31. — Through the nucleus of the III nerve and the most dorsal component of the 

 commissure of the tuberculum posterius containing decussating fibers of tr. tecto-b'jlbaris 

 cruciatus 1. Farther forward the section cuts the ventral thalamus at its widest part and 



