CEREBELLUM OF URODELE AMPHIBL\ 17 



midbrain, these cerebello-tegmental fibers being strictly compara- 

 ble with the internal arcuate fibers arising from the entire length 

 of the somatic sensory area of the medulla oblongata. The more 

 anterior members of this system are directed forward and de- 

 cussate under the midbrain, thus constituting the brachium 

 conjunctivum. 



The dorsal decussation of the velum medullare anterius has the 

 following components (cf. fig. 27) : (1) fine meduUated fibers 

 {com.cb.) connecting the corpora cerebelh of the two sides; (2) 

 unmedullate fibers running in the superficial molecular layer and 

 similarly connecting the two corpora cerebelli {com.cb. I.); (3) 

 tractus spino-cerebellaris ventralis (tr.sp.ch.v.) ; (4) tractus spino- 

 cerebellaris dorsalis (tr.sp.cb.d.), these fibers probably entering 

 the commisure only in ver}^ small numbers; (5) fibers of the mes- 

 encephalic V root (mes.V) ; (6) fibers of the IV nerve root (n.IV). 

 The fifth and sixth of these components have no functional con- 

 nection with the cerebellum. 



I have found no evidence that any root fibers of the V nerve 

 terminate in the cerebellum. The mesencephalic V root tra- 

 verses the cerebellum in many small bundles, some of which de- 

 cussate with the cerebellar commissure; but these fibers all appear 

 to pass through into the tectum mesencephali, there to effect 

 connections with the neurones of the nucleus magnocellularis 

 tecti. 



The anatomical connections of the cerebellum of lower urodeles 

 conform in general to the scheme of cerebellar organization 

 (statotonus hypothesis) recently set forth by Edinger ('12), 

 though in much simplified form, and there are doubtless many 

 additional details still to be worked out. The relations of the 

 area acustico-lateralis and eminentia ventralis cerebelli of uro- 

 deles to the definitive cerebellum of higher vertebrates present 

 problems of considerable interest, whose further investigation is 

 now in process. 



THE JOURXAL OF COMPARATIVE NEUROLOGY, VOL. 24, NO. 1 



