CEREBELLUM 175 



these extends farther forward parallel with the sulcus isthmi as bra- 

 chium conjunctivum. 



In, my earlier papers a ventricular swelling under the cerebellum 

 was termed "eminentia subcerebellaris tegmenti." This has subse- 

 quently been analyzed into several distinctive areas, of which the 

 posterodorsal member was named "eminentia cerebellaris ventralis" 

 ('35a, fig. 1). It is now clear that this is the primordium of the deep 

 nuclei of the cerebellum, and it is here named "nucleus cerebelli" 

 (figs. 2, 10, 32, 33, 91, nvc.cb.). This is an ill-defined region of the in- 

 termediate zone, not clearly separable from its surroundings. Some 

 fibers of the brachium conjunctivum arise from these cells, though 

 only a small part of them. 



The spino-cerebellar tract ascends in company with the spinal lem- 

 niscus, some cerebellar fibers being collaterals of lemniscus fibers, as 

 described above. Cerebellar fibers join this tract from the nucleus of 

 the dorsal funiculus and the sensory zone of the medulla oblongata. 

 One confused issue regarding this tract of Amblystoma can now be 

 clarified. A dorsal slip of the spino-cerebellar tract passing through or 

 above the entering fibers of the sensory V root was described by me 

 ('14, p. 7) and by Larsell ('20, p. 277). These observations could not 

 be confirmed by either of us (Herrick, '14a, p. 375; Larsell, '32, 

 p. 414), the supposed tract being then interpreted as the ascending 

 trigeminal root. It now appears that both the earlier and the later ac- 

 counts are correct. In one of our adult brains, cut in a favorable ob- 

 lique plane (no. 2245), there is partial Golgi impregnation of the sen- 

 sory V root fibers and of the spino-cerebellar tract, with no other 

 fibers stained in this vicinity. A separate fascicle of the ventral spino- 

 cerebellar tract turns dorsally at the level of the V nerve, its fibers 

 interdigitate with those of the entering sensory V root, and rostrally 

 of this level the spino-cerebellar fibers and the ascending sensory V 

 fibers are mingled as far as their entrance into the cerebellar com- 

 missure. Here a fortunate elective impregnation clarifies the confu- 

 sion as neatly as could be done by an experimental degeneration 

 (compare Salamandra as described by Kreht, '30, p. 294). 



In the literature our tractus spino-cerebellaris is sometimes desig- 

 nated "tractus cerebello-spinalis," implying conduction spinalward. 

 Some descending fibers may be present in this tract of Amblystoma, 

 though our preparations have not revealed them. That the larger 

 part of the tract is ascending is clearly evident. 



