284 THE BRAIN OF THE TIGER SALAMANDER 



584). That name is inappropriate for two reasons, first, because few 

 of its fibers reach the bulb and, second, because there is a large 

 tegmento-bulbar tract more ventrally (figs. 27, 28, 29, tr.tecj.h.). The 

 tract here under consideration passes from the posterior part of the 

 dorsal thalamus, eminence of the posterior commissure, and dorsal 

 tegmentum into fascicles of group (7). Its fibers enter f. tegmentalis 

 profundus and end in relation with the small cells of the central 

 nucleus of the isthmic tegmentum. Its entire course is shown in 

 figures 29-33, here marked (7). The isthmic tegmentum is regarded 

 as the pool within which the bulbar reflexes concerned with feeding 

 are organized, and this tract probably plays a critical role in l)ringing 

 to this center the appropriate aft'erents from the intermediate zone. 

 This tract carries only part of the efl^erent fibers from the dorsal teg- 

 mentum. Many of these fibers pass directly ventrally to enter the 

 peduncle and lower tegmental levels uncrossed or with decussation 

 in the ventral commissure. Others ascend or descend in various other 

 tegmental fascicles. 



b) Tractus tecto-bulbaris rectus. — It has recently been found that 

 these fibers leave the tectum by various courses and that many of 

 those from the anterior part of the tectum enter fascicles of group 

 (7), from which they separate in the isthmus to enter the medulla 

 oblongata in company with other tectal fibers (p. 225). These are the 

 fibers which in 1936 were followed from fascicles (7) into the bulb. 



Dorsal fascicles (8). — This conspicuous group contains thick and 

 thin fibers, many of which are well myelinated. Those which come 

 from the postoptic commissure ('36, pp. 304, 338, figs. 4, 8, 17, 18, 

 ■po.{8)) comprise two quite separate systems, («) from the tectum and 

 {})) from the ventral thalanms. The latter are joined by many un- 

 crossed fibers of the same system. 



a) Tractus tecto-thalamicus et hypothahinueus cruciatus i)os- 

 terior. — The coarsest and most heavily myelinated fibers of the com- 

 plex so named in earlier papers, after decussation in the postoptic 

 commissure, enter fascicles of group (8) and distribute to the dorsal, 

 isthmic, and trigeminal tegmentum ('42, p. 221). Other shorter fibers 

 enter fascicles (6) to reach the isthmus, and others end in tlie pe- 

 duncle and hypothalamus. These longer and coarser fibers to the 

 tegmentum were variously interpreted and named in my earlier 

 papers, but good elective impregnations have now clarified their con- 

 nections as tr. tecto-tegmentalis cruciatus. 



b) Trjictus thalamo-tegmentalis ventralis.— As previously men- 



