68 OSBORN. [Vot. II. 
the dorsal roots of the 9th, and from similar sensory cells, 7 sz. 
The lower tract begins at about the same level, and is dis- 
tinguished from the upper by its larger fibres and by a distinct 
contour, but there is some doubt whether it is a motor tract. 
The nucleus, 7 1, is at the angle of the medulla in the same 
position as the supposed motor nucleus of the oth, and is com- 
posed of slightly larger cells than the sensory nucleus, but they 
are not distinctly of the motor character. As represented in 
Figs. 15 and 16, some of them are bipolar; but they have not 
the characteristic multipolar shape and large nuclei which are 
seen in the motor nuclei of the 5th, 5 mz, and 1oth. There 
can be little question, however, from the peripheral distribu- 
tion of this tract that itis motor. The Facial is thus compar- 
atively simple in its origin : unless it is reinforced by the fasciculus 
communis or posterior longitudinal fasciculus, or both, it has, so 
far as observed, no ascending bundle, and in this respect differs 
from the oth, roth, and 5th. It has, however, a small descend- 
ing tract, rising towards the cerebellum above the descending 8th. 
The Trigeminus. Five, or possibly six, tracts are observed 
to enter the Trigeminus, as follows: 1. The ascending tract 
from the cervical region, reinforced by, 2, fibres from the deep 
motor nucleus, representing two tracts. 3. Fibres from the sen- 
sory nucleus. 4. The descending tract from the mesencephalic 
nucleus. 5. The direct encephalic tract. 
(1) The ascending trigeminus is first observed at the 
periphery of the cord, between the lateral and posterior columns, 
and increases rapidly in size, probably by accession of fibres 
from the lateral columns, so that at the exit of the oth pair it is 
the largest of the tracts. (2) At this point we first observe 
fibres entering this tract from the motor nucleus, 5 mz, 
which immediately adjoins the motor nucleus of the gth pair, 
and is external to the group of large ganglion cells which are 
coritinuous with those of the anterior horn. This nucleus in- 
creases in size to the level of the exit of this tract. (3) No sen- 
sory nuclear fibres enter the tract below the level of the exit of 
the 7th pair ; at this point the sensory nucleus appears, 5 sz, 
continuous with that of the 7th, Fig. 17, and the mgtor nucleus, 
which is throughout composed of typical motor cells, immedi- 
ately adjoins it ventrally. The sensory nucleus is very large, 
1 See Appendix, Note 2. 
