CRANIAL NERVES OF SILURUS AND MORMYRUS 21 
fibers of this nerve (also mentioned by that author in the carp 
and by Johnston in Acipenser) were more difficult to trace.'8 
It is interesting that these descending fibers have a course similar 
to and are accompanied by vestibular fibers. This close re- 
lation between fibers of the lateralis and vestibularis nerves is 
also present in other systems of these roots, as will appear from 
the following pages. 
From beneath the crista a large number of arcuate fibers arise 
(figs. 6, 8, 10), which after decussation under the fasciculus 
longitudinalis posterior proceed in a frontal direction, constitut- 
ing the fasciculus longitudinalis lateralis, or lemniscus lateralis, 
which ends in the torus semicircularis or corpus posticum of the 
midbrain. Other fibers, both crossed and uncrossed, seem to 
run in a caudal direction, probably forming a part of the descend- 
ing octavo- or latero-motor system. 
The nervus lateralis anterior enters the brain, as mentioned 
above (p. 9), with the motor and sensory V and sensory VII roots 
(fig. 5). It is the largest part of this complex, lying laterally 
of the sensory VII root, and it consists of a small number of very 
coarse fibers, lying directly on the VII root, and a much greater 
number of finer fibers having a more dorso-lateral position. 
Dorsally of the place of entrance of the nervus lateralis anterior 
we find a region of gray substance which forms the frontal con- 
tinuation of the gray matter of the lobus lateralis posterior and 
is laterally bordered by fibers of the latter, which only disappear 
on a level frontal to the entrance of the nervus lateralis anterior. 
The most frontal bundles of the anterior lateral nerve that 
enter the bulb contain fine fibers only and proceed dorsally in the 
direction of the cerebellum [fig. 11 (1)], where they disappear. 
Their number is fairly large and the fibers, although their neu- 
rites are thin, are very well myelinated. They have also been 
described by Tello in the carp (loc. cit., p. 11). As soon as this 
dorsal root has disappeared in the sections, the other, greater 
18 Compare Tello, El encefalo de los teleosteos. Trabajos del laboratorio de 
Madrid, tomo 7, 1909, fig. 4; and also Johnston, The brain of Acipenser. Zool. 
Jahrb., vol. 15, 1909, p. 24, who traced the descending fibers of this nerve to the 
beginning of the cervical cord. 
