66 OSBORN. [Vou. II. 
as a nerve of special sense, do not in any degree repeat the 
features of the gth and 1oth, which to a certain extent are wit- 
nessed in the 5th and 7th. Of the four distinct roots of the 
8th, I am in some doubt whether the first and last may not be 
given off out of place and ultimately join the 7th. The last of 
these roots may, however, at present be described as a portion 
of the 8th. (4) The fibres of the fourth, or posterior root, are 
received from the posterior longitudinal fasciculus, 
as beautifully shown in the floor of the ventricle of Szvex and 
in sections of this level, Fig. 15. They suddenly turn out 
from the ascending bundle of the fasciculus and traverse the 
medulla at an oblique angle to join the nerve by two small roots. 
Whether studied in transverse or horizontal sections, this is 
clearly an ascending fasciculus, and connects the nerve with the 
lower regions of the medulla or spinal cord, not with the enceph- 
alon. This isanimportant point. (3) Shortly above the exit of 
the oth pair, Fig. 14, a nucleus of large pale ganglion cells 
appears, which is quite distinct from the underlying motor 
nucleus of the 5th. This is the second source of supply 
of the auditory fibres, and probably corresponds to Dezters nu- 
cleus; it is sharply defined from the surrounding cells. (2) In 
the lower angle of the medulla is also seen a group of small 
cells which appears to contribute to this tract of the 8th, 8 sz, 
but cannot be positively determined. (1) On the dorsal side of 
this tract is the bundle of the fasciculus communis, which 
is here double, one-half, VIII., passing outwards to form the 
anterior root of the 8th. (5) As the nerve is given off, a large 
tract is seen which rises external to the sensory nucleus of the 
Trigeminus and constitutes the 8th encephalic tract, which 
is indicated by a contour above fc’’’ in Fig. 17, and by dotted 
lines in Fig. 21. It is possible that this tract sends fibres 
to the mesencephalic sensory cells which may thus form a 
superior nucleus.! 
It is seen that, whatever may prove to be the peripheral 
distribution of the fibres of the fasciculus communis and post- 
erior longitudinal fasciculus, whether to the 7th or 8th, two 
facts remain: first, that the 8th arises ventral to the 
7th, although a purely sensory nerve; second, it 
is inserted in the centre of the Facial-Trigem- 
1It ascends to the midbrain, see Cerebellum 
