64 OSBORN. [Vot. II. 
the lower levels, and increases in distinctness as we ascend. 
The nucleus and bundle of the Glossopharyngeus increases in 
size, and the large ascending bundle of the Trigeminus is thrust 
downwards, Figs. 11 and 12; at the level of the exit of the 
oth pair, the sensory nucleus and upper and lower roots of the 
7th come into view, as well as a third nucleus of the goth, gz, 
which takes the place of the internal nucleus of the roth. 
The fasciculus solitarius has entered the tIoth, also a 
large bundle of the fasciculus communis, fc’, and a fresh 
bundle of this fasciculus is now forming, fc'’. It is noteworthy 
that although the two bundles of the Facial and the Trigeminal 
root are well formed, there is apparently no trace of the Audi- 
tory. Above this level, however, the auditory tract, 8¢, forms 
rapidly between the ascending 5th and the lower 7th tracts. 
It has apparently two nuclei, Fig. 14, and encloses the fas- 
ciculus communis. The Auditory is given off by the 
union of four tracts, and above this the 7th arises by its 
two roots. The upper and lower nuclei of the 7th are then 
replaced by the large sensory nucleus of the 5th, which rapidly 
reinforces the already large ascending tract. A glance at the 
series of figures will show how the sensory nuclei of the gth, 
7th, and 5th pairs replace each other in regular succession, while 
the 8th, so far as observed at present, belongs to a separate 
system. A schematic arrangement of these nuclei is shown in 
Fig. 21, the level at which each transection is taken being 
indicated at the side. 
Glossopharyngeus and Vagus. These nerves are closely related 
to each other; the glossopharyngeus arises dorsally, 
contributing mixed fibres, and the vagus ventrally, 
also contributing mixed fibres. The definite homol- 
ogy of these roots with the 9th and Ioth pairs of the higher 
vertebrates is uncertain. 
The posterior roots of the Vagus, X. ab, 1-5, of this system, 
arise from at least three sources. 1. The fasciculus soli- 
tarius. 2. The fasciculus communis.) 3). A spear 
nucleus in the floor of the 4th ventricle. The two ascending 
fasciculi are both found in the region of the posterior horn. 
(1) The fasciculus solitarius! appears to arise from the 
1 This bundle in the human medulla contributes also to the 9th pair, and extends 
to the level of the 8th Cervical (Krause). Hoffmann-Rauber, Lehr. d. Anat., 1886, p. 
397- 
