Lateral View of Dissected Cerebellum and Brainstem. The cerebellum has been dissected to demonstrate the course of the middle and superior cerebellar peduncles within the cerebellar white matter. The anterior and posterior lobes of the cerebellum are separated by the primary fissure. The arbor vitae is the cerebellar white matter, so called for its branched, tree-like appearance.  The trigeminal nerve attaches to the brainstem at the  junction between the basis pons and the middle cerebellar peduncle. (Image courtesy of M Nunez)