28 H. BERKELBACH VAN DER SPRENKEL 
IV nerve is more advantageously arranged, since the motor cells 
that must be considered as the IV nucleus clearly send out a 
small bundle of myelinated fibers (fig. 13) that turn in a latero- 
dorsal direction around the ventricle in the manner characteristic 
of the IV root. The connection with the extra-medullary root 
can, however, not be stated. The nucleus in question is very 
small and extends through three sections of 25 miera (fig. 13). 
The motor V root, after having entered the bulb, runs in a dorso- 
medial direction. The root is fairly strong, but its fibers are not 
as thick as in Silurus. Its nucleus lies between two parts of the 
fasciculus longitudinalis lateralis (fig. 14), as often occurs in 
teleosts. 
Passing in a caudal direction, the nucleus increases in size 
and, while its dorsal limit remains about the same, the ventral 
cells reach farther downward in the direction of the tegmentum 
of the bulb (fig. 15). The nucleus as a whole acquires by no 
means so ventral a position as in Silurus. 
The sensory V root (fig. 14) enters the brain at the same level 
as the motor root, at first lying laterally of it. Its fibers pro- 
gressively pass over into the bulb and are very thick. The root 
is accompanied by a column of gray substance which is not 
especially enlarged at the proximal extremity of the root, so that 
a distinct frontal sensory nucleus does not exist. 
Shortly after its entrance the descending V tract passes between 
the motor V nucleus (medially) and (laterally) another nucleus 
of large cells in which VIII fibers end and which will be discussed 
later on (fig. 15, n.VIJI1.). Caudally the tract has a more 
dorsal position, lying between the coarse fibers of the VIII root 
dorsally and motor VII fibers ventrally (fig. 16). After this it 
acquires its most medial position (fig. 17) which it soon leaves 
again, being pushed laterad by the communis gray (fig. 19). 
The sensory [X enters the brain running over the spinal V tract 
(fig. 18), but the first X root passes beneath it (fig. 19). Then, 
approaching the spinal cord, it acquires a peripheral position 
and enters the substantia gelatinosa of Rolando. 
As in Silurus, I have not been able to trace the mesencephalic 
root of the V nerve with certainty. I do not, however, doubt 
