George L. Streeter 309 
The frontal ends of the nucleus funiculi teretis and the nucleus inter- 
calatus are cut across in fig. 7. These disappear between figs. 7 and 8. 
Lateral to the nucleus intercalatus is the vestibular field, and lateral 
to that is the nucleus cochlearis, and the stile of the flocculus. In this 
section the nucleus and most of the fibres of the glossopharyngeus have 
disappeared. 
Fig. 8 represents a section through the nucleus of the nervus abducens 
forming, together with the genu of the N. facialis, an elevation ofthe 
floor (eminentia facialis). On one side can be seen the fibre bundles 
of the N. abducens leaving the nucleus. A few fibres connecting the 
nucleus with the superior olive are present. Of the N. facialis three por- 
tions can be seen in this section; the loose strands coming from its 
nucleus, a cross section of the genu, and the nerve trunk in its ventral 
course of exit. Overlapping the N. facialis and the nucleus abducentis 
is the distal extremity of a mass of grey matter, which increases in size as 
we approach the aqueduct of Sylvius. Since as yet we are ignorant con- 
cerning its functien, this structure will be spoken of as the ‘ 
incertus.” 
* nucleus 
At this level the fibres from the nucleus and trunk of the 
vestibular nerve and the restiform body are seen passing dorsally in 
their course to the cerebellum. Some of the more frontal fibres can be 
seen of the root of entrance of the vestibular nerve. 
Fig. 9 is in the trigeminal region, and shows the rvot of that nerve, 
the motor nucleus, and the bundle of decussating fibres, the latter seem- 
ing to pass into the region of the nucleus lying lateral to the posterior 
longitudinal fasciculus. The posterior longitudinal fasciculus, except 
for ependyma, lies at this level exposed in the floor of the ventricle, 
and corresponds to the broadening of the longitudinal median furrow, 
situated in the floor of the ventricle proximal to the eminentia facialis 
(fovea mediana of Retzius). The laver of grey matter seen in previous 
sections and called nucleus incertus is here little changed. In fig. 10, 
however, it is much enlarged in width and thickness. Underlying it 
are the large pigmented cells of the trigeminus (locus coeruleus), and 
mesially is the posterior longitudinal fasciculus. Lateral to it is the 
superior root of the trigeminus. The nucleus consists of a network of 
fine fibres in the meshes of which lie scattered groups of medium sized 
multipolar nerve cells. In its appearance and position it bears a some- 
_ what similar relation to the trigeminus to that which exists between 
the nucleus intercalatus and the vago-glossopharyngeus. It is possible 
that these nuclei, the nucleus incertus and the nucleus intercalatus, 
may represent central sympathetic centers, which we are led to expect 
in the floor of the medulla, as analogous to the grey matter surrounding 
