292 ME. J. L. CLAEKE ON THE INTIMATE STEUCTUEE OE THE BEAIN. 
little upward, and contains nerve-cells of considerable size, collected generally into two 
or three groups, and sparingly scattered at intervals with their longer axes in the direc- 
tion of the fibres. In its course it immediately overlays the grey tubercle (e) enclosing' 
the descending portion of the trigeminus, and is then inserted into the network of the 
outer auditory nucleus (d o ), where it diverges into several bundles. In careful dissec- 
tions and longitudinal sections, the trunk of the nerve in its passage upward and inward 
is seen to wind round the root of the middle peduncle of the cerebellum, where it 
meets and overlays the descending root of the trigeminus contained in the grey tubercle, 
which is itself only the downward continuation of the grey nucleus of the trigeminus, 
first sight the two nerves seem to form a loop with each around the inner side of the 
middle peduncle ; but on closer examination it is found that the auditory nerve passes 
over the descending portion of the trigeminus and enters its own nucleus a little behind 
and to the inner side of the conical mass which forms the nucleus of the large root of 
the fifth. In its passage, however, it is very intimately connected with this nerve and 
the grey tubercle. In fig. 46, Plate XII., there may be observed in the middle of the 
grey tubercle a circular mass or column ( e ) composed of small nerve-cells. In front of 
this and closely connected with it is a beautiful and delicate grey network containing 
small nerve-cells, and enclosing in its meshes the numerous bundles of the descending 
root of the fifth nerve, the cut ends of which are represented by the dark masses. This 
network is continuous behind with the coarser one which forms the outer auditory 
nucleus (d o), and which gives origin to the anterior division of the auditory nerve (P"). 
On the inner side of the grey tubercle, at U, is the group of large multipolar cells com- 
posing the nucleus of the small root of the fifth nerve, and connected by a plexus of fibres 
with the fasciculus teres (K') ; and in front of this nucleus and of the grey tubercle is a 
broad band of arciform fibres (p" p"') which proceed from the restiform body and middle 
peduncle at p\ to sweep round and diverge into the central parts of the medulla. Fig. 
47, Plate XII. represents a dissection of the left side of the medulla and of the fourth 
ventricle, showing the anatomical relations of these and other parts. The dissection was 
made by first removing the epithelium on the posterior pyramid and peeling off the 
posterior root of the auditory nerve from without inward, including the inner nucleus 
in which it ends. The restiform body or inferior peduncle (c d) of the cerebellum, and 
the middle peduncle were then drawn gently away or aside from the central portion 
of the ventricle, and pressed a little downward, exposing a somewhat triangular space 
which is divided into two unequal parts (A', B') by the large root (C") of the fifth nerve 
in its passage to the conical eminence or nucleus (D') which projects from the side of the 
ventricle. The descending prolongation of this nucleus with the descending portion of 
the nerve, constituting together the grey tubercle (e) of fig. 46, are seen to be overlaid 
by the anterior division (P") of the auditory nerve, as it passes obliquely upward and 
inward to its nucleus beneath i, which is the concavity left by the removal of the inner 
auditory nucleus with the posterior division of the nerve. The anterior and under 
portion of the trigeminal nucleus (D'), where it is connected with the point of the fillet 
