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convinced that this tract is identical with the mesial bundles of the 

 radix mesencephalica trigemini. It certainly has no relation to the 

 tractus tecto-cerebellaris of Acipenser. If the nucleus niagnocellularis 

 tecti and Reissner's fiber form an optic reflex apparatus, as Sargent 

 thinks, it is very diflicult to see why processes from the same cells 

 should enter the trigeminus nerve. 



The writer in studying the brain of Acipenser (9) did not agree 

 with GoRONOWiTSCH but came to the conclusion that all the ascend- 

 ing fibers of the trigeminus turned into the cerebellum, or ended 

 in the acusticum. Since the bundle has been followed in Scyllium 

 the Acipenser preparations have been reviewed and the writer finds 

 that GoRONOWiTSCH was entirely right. The course of the bundle is 

 as follows. The sensory root of the trigeminus, as previously described, 

 runs deep into the acusticum and divides into ascending and de- 

 scending tracts. The spinal Vth tract is small; the great majority 

 of the fibers go into the deeper parts of the acusticum. Near the 

 internal surface of the acusticum a bundle of very coarse fibers col- 

 lects and runs forward mesial to the body of the ascending tract. 

 These fibers are nearly as large and quite as conspicuous in trans- 

 verse sections as the fibers of the fasciculus longitudinalis dorsalis. 

 At the junction of the oblongata, cerebellum and tectum the thickness 

 of the brain wall is enormously greater than in Scyllium and the 

 structure is correspondingly complex. The thick acusticum has a 

 broad connection with the granular layer of the median body of the cere- 

 bellum and also with the lateral lobes. At the same time the large 

 secondary vagus nucleus crowds up against the acusticum from in front 

 and below and sends a commissure through the body of the cerebellum. 

 The tectum also is thick and sends a tract into the cerebellum, and 

 a complex series of tracts from the inferior lobes pass through this 

 region, partly entering the cerebellum. As the ascending tract of the 

 trigeminus reaches the junction of the acusticum with the body of the 

 cerebellum, the greater part of the medium sized fibers bend mesad 

 into the body of the cerebellum. As they do so they cross the bundle 

 of coarse fibers, which continue forward and upward. The course of 

 the bundle is direct and since the fibers are much coarser than any 

 other in this region, they are traced without doubt. They plunge 

 straight through all the intermingled tracts in this region and gain 

 the lower part of the torus semicircularis of the mesencephalon. Here 

 they lie adjacent to the ventricle among the cells of the torus and 

 continue forward. The bundle now spreads somewhat dorsally and a 

 part of its fibers go into the tectum proper, but the greater part of 



Anat. Anz. SXVII. Auisätze. 24 



