244 A MANUAL OF ANATOMY. 



an unnecessary refinement of description into seven other 

 lobules. 



The cerebellum is connected to the rest of the brain by 

 three pairs of nerve-bundles, or peduncles : the superior, 

 middle, and inferior. 



The middle peduncles have already been referred to as 

 the great transverse commissure or the pons, which unite 

 the two hemispheres of the cerebellum in front of the fibres 

 of the crura cerebri. 



The superior peduncles are flattened bundles which 

 project backward and outward from the testes of the corpora 

 quadrigemina to reach the cerebellum internal to, and in 

 front of, the middle peduncles. 



The superior peduncles are united across the median line 

 and from the posterior margin of the quadrigeminal lamina 

 to the front of the under surface of the cerebellum by a 

 thin sheet of white matter called the valve of Vieussens, 

 or the superior medullary velum. A tongue-shaped pro- 

 jection the lingula from the superior vermiform process 

 of the cerebellum rests upon the posterior part of the velum. 



An extension of some fibres from the valve of Vieussens 

 forward between the posterior pair of quadrigeminal bodies 

 is called the frenulum veli. 



The inferior peduncles of the cerebellum connect it with 

 the lateral regions of the posterior part of the medulla. 

 They are formed of the fibres from the direct cerebellar 

 tract, the internal and the external arciform fibres, and go 

 under the name of the restiform tracts. They enter the 

 cerebellum internal to and behind the middle peduncles. 



On sections of the cerebellum the peculiar arrangement 

 of its white matter within the gray gives the appearance of 

 a branching tree, hence the name of arbor vitse which is 

 applied to it. 



