CRANIAL NERVES OF SILURUS AND MORMYRUS 17 
part of the lobe—not from the dorso-medial part—and cross the 
dorsal part of the raphé. It is difficult to trace them separately 
because they mingle with or are covered by dorsal arcuate fibers 
from the tuberculum acusticum. There are not very many of 
these fibers, but their presence is easily demonstrable. Herrick 
considers them as reflex fibers for the cervical cord, which is 
probable on account of their position in or next to the highway 
of motor reflex fibers, the fasciculus longitudinalis posterior.1 
The motor roots of the vagus enter the brain some distance in 
front of the sensory roots, as was also the case with the motor IX. 
Their place of entrance is also more ventral. This separation 
is more conspicuous in the frontal vagus root than in the more 
caudal roots. 
The motor roots run in a fronto-medial direction, their nucleus 
being located dorsally near the floor of the fourth ventricle 
(fig. 4). In the frontal extremity of the nucleus some of the 
cells exhibit a tendency to shift in a ventral direction (fig. 10). 
In more caudal levels the nucleus acquires a more dorsal position. 
The column is divided into some smaller cell groups fairly 
well separated from each other. In most cases each of these 
groups corresponds with a rootlet (fig. 4). Outside the brain 
stem the rootlets join and leave the bulb as one trunk. The 
frontal rootlets of the motor X run under or through the second- 
ary gustatory tract, the caudal rootlets over it leaving the brain 
at a more dorsal level. 
The sensory vagus has two roots, of which only the caudal one 
contains somatic fibers that join the descending V root. The 
rest of the sensory X contains also two sorts of fibers,!® just 
like the sensory IX. The thinner fibers provided with small 
4C. J. Herrick. These fibers are considerably hypertrophied in the codfish 
and probably have an influence on the movement of the pectoral fins, which in 
this animal are important instruments for taste exploration. Compare C. J. 
Herrick. A study of the vagal lobes and funicular nuclei of the brain of the cod- 
fish. Jour. Comp. Neur., vol. 17, 1907, p. 67. 
15 When dealing with the sensory VII and sensory IX, I mentioned also capsular 
fibers. These are not absent in the vagus, but seem to be connected with the 
dorso-medial system which probably also serves gustatory impulses. The medial 
branch represents Herrick’s ‘deep root’ of the communis nerves, if I understand 
him well. 
