(b) 
(c) 
(d) 
THE CENTRAL NERVOUS SYSTEM. 279 
nected forwards with the cerebral aqueduct and backwards 
with the central canal of the spinal cord. Its roof is formed 
principally by the anterior and posterior medullary vela, the 
latter being attached to the cerebellum close to one another, 
so that they underlie it. 
The rhomboid fossa (fossa rhomboidea) is the shallow 
depression enclosed by the thick lateral and anterior walls 
and floor of the ventricle. The middle line shows a narrow 
depression, the posterior 
median fissure (fissura 
mediana posterior), on either 
side of which the floor is 
raised into a low ridge, de- 
scribed as the medial emi- 
nence (eminentia media- 
lis). The posterior end of 
the fossa forms with the 
enclosing wall the somewhat 
triangular figure described 
as the calamus scriptorius 
The lateral supports of the 
cerebellum, now represented 
by their cut ends, are 
formed by fibre-bands pass- 
ing into the cerebellum from 
adjacent ventral portions of 
the- brains Inteach a middle? . grat vems aren race eee 
band, the brachium pon- ip "brachim pontis; “cl. chan; li 
bis ptenters athe: pons’, atl)liecticrm body. “ean metal Cothcace: 
anterior band, the. brach- gracilis; gmp, posteee median fexine of 
LUI COMJUNCHVUINS “C=nistcs. Gece: Tcnecn tices ok ke 
fersi. ther mesencephalon... satus state dene ee 
while a posterior connection 
is established with the medulla through the restiform body. 
The lateral wall of the fossa is formed by a thick ridge of 
nervous matter, convex on its medial side, the restiform 
body (corpus restiforme). Its anterior portion bears a large 
spherical elevation overlying the origin of the acoustic nerve. 

