The Cranial Nerve Components of Petromyzon. 163 
three or four fibers. A communication of two or three fibers between 
the sympathetic and the ganglionated vagus trunk is found at 467, 
where the two run close together. At 502 the left sympathetie gives 
off a branch which is traced to the mucosa. Other fibers must be 
distributed singly or in very small bundles to the mucosa, vessels, 
ete. The first part of this trunk is drawn by Harschrk in Fig. 11, 
but not named. Its position is shown in Figs. 10—15. 
For the sake of celearness it will be well to review the arrange- 
ment of the components in the roots and ganglia of the VII—VII 
complex. The acustiecus root is much the largest and least dense, 
and it extends farther caudally than the others. Its fibers are medium 
sized and its ganglion cells spindle shaped and very slender. It also 
contains a few very coarse fibers and very large ganglion cells. The 
acusticus ganglion makes up the caudal and lateral portions of the 
intra-capsular ganglion and from its lateral border rami branch out 
to the auditory epithelium. Beneath the acusticus root the general 
eutaneous, motor and fasciculus communis roots leave the brain 
somewhat mingled. The general eutaneous root is the most caudal 
and ventral and the motor and communis components follow upward 
and forward in the order named. These three enter the mesial part 
of the intra-capsular ganglion and the general cutaneous and com- 
munis fibers probably bave all their ganglion cells in this ganglion. 
All the fibers from this median, large-celled ganglion pass through 
the foramen in the floor of the auditory capsule and form the sym- 
pathetic and the visceral sensory, visceral motor and general cutaneous 
components of the hyomandibular ramus as above described. The 
most cephalie roots of the complex are the dorsal, neuromast roots. 
These go directly down over the cephaliec surface of the intra-capsular 
ganglion and through the cephalie part of the foramen and have 
their ganglion cells in the two ganglia beneath the auditory capsule. 
The small caudal one of these ganglia supplies the neuromast com- 
ponents for the hyomandibular nerve; the large anterior ganglion 
gives rise to the infraorbital and supraorbital rami. It is very inter- 
esting to note that the ganglia of the pre-auditory neuromast rami, 
which arise (26) from placodes in connection with the trigeminus and 
profundus ganglia are excluded from the auditory capsule and for 
the most part lie in front of it, while the other ganglia are all three 
ineluded within the capsule. 
