66 J. B. JOHNSTON, 
partial obliteration of the groove of the ventral horn are due to the 
end nucleus of the bundles of MEYNERT. About.opposite the caudal 
border of the cerebellum there is at either side of the fasciculus 
longitudinalis posterior, lateral to the grooves of the ventral horns, 
a low elevation of considerable cephalo-caudal extent formed by the 
motor nucleus of the V nerve. It is clearly seen in Phot. 7. 
In dorsal view the lobi vagi appear to bound the IV ventricle 
dorso-laterally. These lobes are long fusiform ridges marked by 
numerous small thickenings which are largest in the middle part of 
the lobes and are entirely absent in their cephalic one-third. The 
small thickenings mark the points of entrance of the principal root- 
lets of the. X nerve, while the entrance of the IX causes a much 
larger thickening which is clearly seen in Phot. 3, a short distance 
caudal to the lobus lineae lateralis. Cephalad from the IX nerve 
the lobes consist chiefly of the root fibres of the dorsal VII, and 
the lobes terminate abruptly cephalad at the point of entrance of 
that nerve root. In median view (Phot. 3) a small ridge continues 
forward from the cephalic end of the lobus vagi and ends in a 
slight enlargement in the lateral wall beneath the cerebellum. This 
is not, as GORONOWITSCH (89) stated, a cerebellar component 
of the dorsal VII, but is formed of VIII and V fibres, and the 
enlargement is part of the median V nucleus to be described below 
(page 77). ; 
Dorso-lateral to the lobus vagi there appears, a short distance 
cephalad from the calamus, a small ridge which rapidly enlarges as 
it passes forward, partly covers the lobus vagi dorsally, and at the 
cephalic end of the medulla is surmounted by a large body which 
forms the whole thickness of the lateral wall at its dorsal border. 
These are the tuberculum acusticum and the lobus lineae lateralis 
respectively. The lobus lineae lateralis is marked by conspicuous 
irregular transverse ridges and furrows. In median view (Phots. 2 
and 3) the acusticum seems to emerge from behind the lobus vagi 
as the latter decreases in size, and does not rise higher dorsad than 
the highest point of the lobus vagi. The lobus lineae lateralis is wholly 
dorsal to the acusticum and is separated from it by a well-marked 
groove, which indicates the position of the cerebellar crest. On the 
internal face of the acusticum are seen a number of small vertical 
ridges or striations. These are formed by root fibres of the lateral 
line nerves and by arcuate fibres to the base of the medulla as 
described in a later section (page 82). They are most prominent at 
