GANGLIA AND NERVES OF SQUALUS 51 
37. RAMUS VISCERALIS X 
There is in the specimen plotted no ramus visceralis arising 
from the posterior end of the ganglion visceralis X; such as 
Neal (14, plate 7, fig. 36) plots in a 25 mm. embryo. Neither 
is there in my 25 mm. embryo any well defined ramus visceralis 
or vagus nerve, although the posterior end of this ganglion is 
ragged and seems to give rise to a very immature nerve trunk. 
This is rather surprising in view of the condition of the first 
two spinal nerves and the anterior sympathetic ganglia and 
rami communicantes, all of which are well formed in the 22 mm. . 
embryo. There are several minute twigs arising from the ven- 
tral and mesial surfaces of this ganglion but their destination 
could not be determined. Their general course is mesial but 
they are quite short. 
In a 30 mm. embryo, however, the ramus visceralis X (fig. 1, 
R.Vis. X) is well formed and runs directly ventrad and caudad 
and has the usual distribution of the vagus nerve. 
SUMMARY AND DISCUSSION 
Squalus acanthias possesses at the stage of 22 mm. eighteen 
separate cerebral ganglia. Of these eighteen ganglia the gan- 
glia profundus, Gasserian, lateralis VII dorsalis, and acusticus, 
are isolated so that the nerves arising from them are pure and 
readily identified. The remaining ganglia are in contact with 
and sometimes fused with other ganglia so that, while they can 
be identified, they are not separate as are those mentioned 
above. The nerves arising from these ganglia which are in 
contact are mixed with motor fibers only except in the follow- 
ing cases. The nervus terminalis is combined with the olfac- 
tory, the ramus auricularis X seems to be fused with the ramus 
lateralis X,, and the hyomandibularis contains both lateralis 
and visceral sensory fibers. The following table gives schemati- 
cally the ganglia and rami as identified. 
The nervus terminalis is placed provisionally under the general 
cutaneous component where it is classified by Johnston (’06, p. 
106). Brookover (’10), however, presents strong evidence for 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 27, NO. 1 
