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them appear to end in the region of the torus. The identification of 

 the bundle as a part of the sensory root of the trigeminus and the 

 tracing of its course are both quite as clear as in Scyllium. It 

 appears doubtful whether any of the fibers come near the nucleus 

 niagnocellularis. 



The writer has studied this tract in two series of transverse sec- 

 tions of the brain of Necturus. The brains were fixed by vom Rath's 

 picro-osmium-platino-acetic mixture, which blackens the sheaths, and 

 the sections were sharply after-stained with acid fuchsin. The sheaths 

 are better fixed than in bichromate of potassium and the preparations 

 give excellent Weigeet effects. The method is admirable for small 

 brains. The coarse fibers of the sensory root of the trigeminus on 

 entering the oblongata run mesad through the acusticum and turn 

 forward next to the cavity. In Necturus the motor root bundles are 

 ventral to the sensory and quite distinct from them. Fig. 5 shows 

 the relation of the coarse fibers to the sensory root. As the tract 

 runs forward it forms several diffuse small bundles lying ventro-lateral 

 to the ventricle (Fig. 6). The ventro-mesial bundles consist of the 

 coarsest fibers. They are thicker than the fibers of the fasciculus 

 longitudinalis dorsalis, but their sheaths are not quite so thick. The 

 position of the bundle with regard to the ventricle and the tuberculum 

 acusticum is identical in Scyllium, Acipenser and Necturus, and in all 

 it corresponds as closely as possible with that in man. When the 

 junction of the cerebellum and tectum are reached the tract has col- 

 lected into a compact bundle (Fig. 7), which is imbedded in the thick- 

 ness of the brain wall. The bundle now turns dorsally and divides 

 into mesial and lateral parts. The lateral part is finer fibered. It 

 arches up around the lateral lobe of the cerebellum close to the 

 junction with the tectum (velum), and forms a commissure in the 

 dorsal wall of the cerebellum which in Necturus lies forward over the 

 tectum opticum (Fig. 8), As the bundle ascends in the cerebellum it 

 gives off two bundles, one near the base of the tectum and one near 

 the dorsal surface, which penetrate the tectum to its cellular zone and 

 run forward (Fig, 7). In Fig. 7 the fine fibers of the fiber zone of 

 the tectum (tractus tecto-bulbaris and dorsal decussation) are shown 

 crossing these small bundles. The fibers continue forward, gradually 

 growing less numerous, and a few fibers at the cephalic border of the 

 tectum seem to cross in the dorsal decussation. The mesial bundle 

 is larger and contains the coarser fibers. It continues forward and 

 upward into the cellular zone of the tectum (Fig, 8) in which the 

 fibers spread widely and soon lose their sheaths. Only a very few of 



