70 journal of Coniparative Neurology and Psychology. 



of the brain, I mention the important tracts to the deeper layers 

 of the tectum opticum, the fibrce te dales or lemniscus, of which I 

 have already mentioned when describing the mid-brain that after 

 decussating they deliver a contingent of fibers to the cerebellum. 

 This is the reason w^hy its fibers are not so numerous in the oblon- 

 gata as in the mid-brain. Its fibers at the beginning of the 

 oblongata are all situated ventrally of the superficial origin of the 

 trochlearis (see Fig. Ixxxvii) and at the entrance of the trigeminus 

 also they are all situated ventrally of the fifth root. During this 

 part of their course the fibers do not diminish in number. Fur- 

 ther down, however, they diminish and one separate bundle bends 

 inward from the most laterally situated group and can be traced 

 into the abducens nucleus. This agrees with Auerbach's state- 

 ment that he saw tectal fibers end in the oculomotorius and tro- 

 chlearis nuclei, as Haller afterward confirmed (Fig. xcii). That 

 I was not able to make the latter observation myself I explain as 

 due to a less fortunate direction of my sections at that point, for in 

 view of the certainty with which I can demonstrate this connection 

 for the abducens nucleus I can no longer doubt these statements, 

 the more so as physiologically it can awaken no surprise that cen- 

 trifugal fibers of the tectum should pass toward the nuclei of the 

 eye-muscle nerves. 



These fibers, however, form only a very small part of this 

 enormous ventro-lateral mass of fibers about whose exact ter- 

 minations the statements of authors differ. Edinger conceives 

 that they end in the nuclei of the sensory nerves and accordingly 

 would form a centripetal tract in which in the higher animals it is 

 possible to trace even the different fascicles from each sensory 

 nucleus separately. Haller is of a different opinion and con- 

 siders them as connections between the tectum and secondary 

 motor regions, as far as I can make out his meaning. The unde- 

 cussated groups of the lemniscus situated laterally which give off 

 the abducens tract described above decrease greatly between the 

 region of the trigeminus and the acustico-facialis, as Mayser has 

 already noted {cj. Figs. Ixxxix and xcii, Plate VI). In this same 

 region a gray mass is formed ventrally which contains only small 

 cells and was described also by Haller and there is no doubt that 

 these fibers end here. This gray mass extends very nearly dow^n 

 to the glossopharyngeus and vagus, but is most extensively devel- 

 oped about the tuberculum acusticum (Figs, xciv to xcvi). At 



