156 Development of Ear and VII-VIII Cranial Nerves 
of the ganglion connecting it with the brain consists of a single stem. 
Owing to the proximity of the ganglion mass to the ear vesicle the nerves 
uniting them are at this time very short. His, Jr., 89, p. 6, regards that 
portion of the ganglion which we have called the pars inferior as the 
ganglion cochleare. What I regard as the ganglion cochleare or ganglion 
spirale does not make its appearance until a trifle later, in embryos of 
about 9mm. ‘There can be seen then a group of ganglion cells massing 
themselves on the ventral border of the pars inferior, which corresponds 
completely to the future spiral ganglion and may be considered as its 
anlage. This anlage develops into a derivative which buds off from 
the pars inferior and then follows an individual course of growth in- 
dependent of the latter, and this is analogous to the way in which we 
have already seen the membranous cochlea bud off from the saccule and 
develop independently. 
That part of the pars inferior which does not participate in the forma- 
tion of the spiral ganglion remains closely related to the pars superior, 
and supplies the saccule and posterior ampulla. It is this that His, Jr., 
describes in a later stage as the Zwischenganglion, and whose centripetal 
fibers he joins to those of the main cochlear trunk. 
In embryos of 20 mm. (compare Figs. 1, m, n, Plate I) the pars 
superior has increased greatly in size, and its peripheral nerves, which 
before were massed together, have become separate and distinct branches. 
The pars inferior, from which the spiral ganglion is rapidly separating, 
consists of a connecting strand of ganglion cells giving off separated 
branches to the saccule and posterior ampulla. The fibers extending to 
the posterior ampulla are at first (embryos of 11 mm.) loosely spread 
out and give the appearance of more than one nerve, but later, either by 
atrophy of some of them or by becoming bundled together more closely, 
they constitute a single compact nerve. It is possible that here we have 
to do with temporary fibers representing branches to the additional nerve 
endings which are found in this region in lower forms. 
- The cochlear nerve can be distinctly seen collecting its fibers from the 
spiral ganglion and extending up toward the brain. The exact manner 
in which this nerve reaches the neural tube proved difficult to determine. 
It apparently sprouts out from the spiral ganglion and travels up on 
the median surface of the vestibular ganglion until it reaches the brain. 
To be certain of this would require a greater number of stages between 
8 and 10 mm. than were available. In the embryos studied the proximal 
end of the nerve could be made out almost as soon as the distal. So it 
is possible that the cochlear trunk consists originally of a column of 
