160 Development of Ear and VII-VIII Cranial Nerves 
a terminal plexus in the substance of the tongue. We are thus indebted 
to this writer for establishing the fact that the nerve of Wrisberg, or pars 
intermedius, and the chorda tympani, are two continuous parts of the 
same nerve, connecting the anterior part of the tongue with the floor of 
the fourth ventricle, an essential fact which has been very slow in 
getting into our text books. Further details regarding the central path 
of this nerve is given in a supplementary note in a paper of His, go, 
in description of a 17 mm. human embryo. He reports this nerve as 
extending from the geniculate ganglion as an independent bundle into 
the brain, where it can be seen running along the median edge of the 
acoustic area spinalwards until it reaches the entering fibers of the 
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G. genic. et pars intermed. 
Fic. 6. Sagittal section of a 7 mm. human embryo (B. 17), showing the 
relations of the facial-acoustic complex. 
glossopharyngeus. It joins with these fibers and together with them 
takes part in the formation of the tractus solitarius. His felt justified 
in assuming that we have here to deal with a union within the neural 
tube of the taste fibers from the anterior and posterior portions of the 
tongue, one group coming through the chorda tympani and nerve of 
Wrisberg, and the other through the glossopharyngeus. This view has 
since then been vigorously supported by Dixon, 99, who pictures the 
facial nerve as a typical branchial nerve developed in connection with 
the ear cleft, having a motor part behind the cleft supplying the muscles 
developed from this arch, and a sensory part made up of the chorda 
tympani and great superficial petrosal which consist almost entirely of 
