The membranes and vessels are removed. _C_, Central white matter
(corpus medullare) of cerebellum; _P.c._, cerebral peduncle; _C.q._,
corpora quadrigemina; _P_, pineal body; _Th._, thalamus; _V.III._,
third ventricle; _r_, optic recess; _r′_, infundibular recess;
_C.m._, mammillary body; _s_, subcallosal gyrus; _A.p._, area
parolfactoria; _G_, genu of corpus callosum; _S_, splenium of same;
_1_, callosal sulcus; _2_, interventricular foramen; _3_, olfactory
bulb. The cerebral lobe of the pituitary body is distinguished by
its lighter color.
]
When the tela is pulled out one may easily get the impression that the
lateral ventricle communicates with the exterior by means of the
chorioid fissure. Such is not the case, since the chorioid plexus is
covered by the epithelial lining of the ventricle, which has been torn
away.
The =rhinencephalon= or olfactory part of the brain comprises the
olfactory bulb, peduncle and tracts or roots, the trigonum olfactorium,
the area parolfactoria, and the pyriform lobe.[199]
The =olfactory bulb= (Bulbus olfactorius) is an oval enlargement which
curves upward in front of the frontal pole of the hemisphere. Its convex
superficial face fits into the ethmoidal fossa and receives numerous
olfactory nerve-fibers through the cribriform plate; hence it is very
difficult to remove the bulb intact. It contains a considerable =cavity=
(Ventriculus bulbi olfactorii) which is connected with the lateral
ventricle by a small canal in the middle olfactory tract. The deep face
is largely in contact with the frontal pole of the hemisphere and is
connected with the olfactory peduncle.
The gray matter of the bulb is external and is thickest on the convex
anterior surface. The posterior surface consists to a large extent of
fibers which are the axones of the mitral cells of the deep layer of
the gray substance and go to form the peduncle and striæ.
The =olfactory peduncle= (Tractus olfactorius) is a very short but wide
band of white substance which arises in the olfactory bulb and extends
back to be continued by the olfactory tracts.
[Illustration: