Efferent fibers of the deep cerebellar nuclei in hedgehogs

Three main deep cerbellar nuclei are apparent in hedgehogs belonging to the genera Erinaceus and Hemiechinus ; however, at various levels they exhibit a considerable continuity with one another. Electrolytic unilateral lesions were placed in the deep cerebellar nuclei of these hedgehogs, and additional animals were subjected to a midline incision of the cerebellum between the two fastigial nuclei. Degenerating axons were traced from the sites of lesions using the Nauta and Fink‐Heimer techniques. The typical mammalian pattern is evident in the distribution of the cerebellifugal fibers of the hedgehog. Crossed and uncrossed fastigial efferent fibers are directed primarily toward vestibular nuclei and the bulbar reticular formation except for a relatively small ascending limb of the uncinate fasciculus. The brachium conjunctivum originates from the nucleus interpositus and nucleus lateralis. The efferents of these nuclei are directed rostrally to the contralateral red nucleus. Fibers passing beyond the level of the red nucleus terminate in the thalamic nuclei. Fibers from the brachium conjunctivun also supply the inferior and superior colliculi. Axons forming the descending limb of the brachium conjunctivum are divided into medial and lateral fascicles.