122 THE POCKET ANATOMY 



the ventricle it is thickened by white matter, and is termed 

 the ligula ; and at the apex of the calamus another thickening, 

 the obex, occurs. Projecting from the roof on each side of 

 the middle line is the choroid plexus. 



In the upper half, the roof is formed by the converging 

 superior peduncles of the cerebellum and the intermediate 

 superior medullary velum or valve of Vieussens, continuous with 

 the white matter of the cerebellum. Grey linear thickenings 

 on the valve of Vieussens, continuous with the grey cerebellar 

 cortex, constitute the lingula. 



BOUNDARIES OF THE 4*TH VENTRICLE. 



Laterally. Floor. Roof. 

 | f Clavseoffuniculigraciles. Medulla (below . Pia mater (below). 



"^ -? Funiculi cuneati. Nodule of inferior vermi- 



^ ^ Restiform bodies. Pons (above). form process. 



^ ,- Valve of Vieussens, and 



I Superior peduncles of Superior peduncles of 



"* \ cerebellum. cerebellum (above). 



Grey Matter of the Medulla. 



1. Remains of grey matter of cord. 



(a) Grey tubercle of Rolando, from posterior cornu, 



appears in front of restiform body. 



(b) Remains of grey commissure, part continued into 



vagus and auditory nuclei , and part into fasciculus 

 teres. 



(c) Remains of anterior cornu, intersected by white 



fibres, giving rise to the formatio reticularis of 

 medulla. 



2. bpecial deposits of grey matter. 



(a) Nucleus of hypoglossal. 



(b) Nucleus for accessory part of spinal accessory. 



(c) Nucleus of vagus, passing above, under auditory 



nucleus, into nucleus of glosso-pharyngeal. 



(d) Nucleus of glosso-pharyngeal. 



(e) Nucleus of auditory nerve. 



(/) Corpus dentatum, or nucleus of the olivary body. 

 (g) Accessory olivary nucleus. 



THE PONS VAROLII. 



Position. Placed above the medulla, below the cruracerebri, 



and between the lateral halves of the cerebellum. 



