CEREBELLUM 489 



largest of the three. It is formed by the transverse fibres of 

 the pons, and it enters the cerebellar hemisphere on the 

 lateral side of the other two. The lips of the anterior part 

 of the horizontal sulcus are separated widely from each other 

 to give it admission (Fig. 195). 



The inferior peduncle is the restiform body of the medulla 

 oblongata. As it leaves the dorsum of the medulla oblongata 

 it turns sharply backwards and enters the cerebellum between 

 the other two peduncles. 



The superior peduncles are the brachia conjunctiva of the 

 cerebellum. They are composed of fibres which come, for 

 the most part, from the nucleus dentatus of the cerebellar 

 hemisphere. As they issue from the cerebellum, the 

 peduncles lie close to the medial sides of the corresponding 

 middle peduncles. They then proceed upwards towards the 

 inferior pair of quadrigeminal bodies. At first, they form the 

 lateral boundaries of the upper part of the fourth ventricle, 

 but they converge, as they ascend on the dorsal aspect of the 

 pons, so that ultimately they overhang the fourth ventricle 

 and enter into the formation of its roof. They disappear 

 under cover of the inferior colliculi of the quadrigeminal 

 lamina, and their course in the mesencephalon has been 

 described already (Figs. 180, 181, 194, 195) (p. 45?)- 



Medullary Vela. The medullary vela are closely associated 

 with the peduncles. They consist of two thin laminae of 

 white matter which are projected out from the white central 

 core of the cerebellum. The anterior medullary velum stretches 

 across the interval between the two brachia conjunctiva 

 (superior peduncles), with the medial margins of which it is 

 directly continuous. " It is triangular in form, and is con- 

 tinuous below with the white matter of the cerebellum. 

 Spread out on its dorsal surface is the tongue-shaped prolonga- 

 tion of grey matter from the cortex of the cerebellum which 

 is termed the lingula, and issuing from its substance, close 

 to the inferior colliculi of the quadrigeminal lamina, are the 

 two trochlear nerves. 



*\}\e posterior medullary velum is somewhat more complicated 

 in its connections. It presents the same relation to the 

 nodule that the anterior velum presents to the lingula. It is 

 a wide thin lamina of white matter so thin that it is 

 translucent which is prolonged out from the white centre 

 of the cerebellum above the nodule. From the nodule it 



