THE CEREBELLUM 



211 



THE EFFERENT CEREBELLAR TRACTS 



The efferent cerebellar tracts arise in the central nuclei. It is probable that 

 no fibers of cortical origin leave the cerebellum except, perhaps, some to Deiter's 

 nucleus (Clarke and Horsley, 1905). 



The brachium conjunctivum, or tractus cerebellotegmentalis mesencephali, 

 arises for the most part at least in the dentate nucleus and terminates in the red 

 nucleus and thalamus of the opposite side (Fig. 153). It constitutes the chief 

 tract leading from the cerebellum and has been more fully described on page 

 159. It undergoes a complete decussation beneath the inferior colliculus in 

 the tegmentum of the mesencephalon. Both before and after this crossing its 



Brachium conjunctivum 



Thalamus 



-Red nucleus 

 Nucleus fastigii 



TV Nucleus dentatus 



Fastigiobulbar tract 



- Tractus cerebellotegmentalis 



pontis 



Lateral vestibtilar nucleus 



Fastigiobulbar tract 



Fig. 153. Efferent tracts which arise in the central nuclei of the cerebellum. (Modified from 



Edinger.) 



fibers give off branches, which descend in the reticular formation of the pons 

 and medulla. Some of the impulses reach the thalamus, but the others are 

 relayed in the red nucleus along the rubrospinal and rubroreticular tracts to 

 motor neurons in the brain stem and spinal cord (Fig. 115). 



Other efferent tracts arise in the nucleus fastigii of the same and opposite 

 side, and run, probably by way of all three cerebellar peduncles, to the retic- 

 ular formation of the pons and medulla oblongata. One bundle of these fibers 

 winds around the brachium conjunctivum before descending through the pons 

 and medulla (Fig. 153). It is probable that other fibers descend by way of the 

 restiform body, and are distributed in the reticular formation of the medulla 



