162 
ON THE ORGAN OF HEARING 
The posterior branch or nerve separates from the sabu- 
lous nerve, as soon as it enters the vestibule, and, diving 
into a small foramen, is separated from the plexus by a 
thin cartilaginous septum, which, being transparent, allows 
of the posterior nerve being seen through the cartilage, and 
thus causes the above appearance. 
This nerve proceeds in a direct line, until it arrives near 
the ampulla of the posterior canal, where it emerges and 
divides into two branches, the filaments of which embrace 
and perforate each side of the membranous ampulla, on the 
inside of which they are distributed in a similar manner to 
the superior-anterior branch on that of the anterior am- 
pulla. 
As soon as the sabulous nerve has given off the posterior 
branch, it runs outwards, and rather backwards, gives off 
numerous slender branches (that run forwards), and, as it 
advances, gives off a large branch, containing above one- 
third of its filaments; which branch runs outwards, and 
rather forwards, and divides in numerous branches that 
unite with a strong nerve of a semicircular figure. This 
nerve, which may be termed the Nervus communicans, from 
its uniting with most of the branches of the plexus, extends 
from the fossa angoriana the whole length of the vestibule ; 
the one extremity assisting in forming the cornu, and the 
other uniting with a small branch, given off by the sabu- 
lous nerve, as it enters the vestibule. 
This communicating nerve gives off numerous short 
twigs which run forwards, supply the anterior parts of the 
vestibule, and contribute materially in forming the plexus. 
It likewise unites with a small nerve, that enters a fora- 
men about three or four lines anterior to the meatus inter- 
nus, and which, passing outwards, arrives in the oblong- 
depression situated under the anterior edge of the plexus, 
