162 Development of Ear and VII-VIII Cranial Nerves 
essential points has been published by Weigner, 05, who studied serial 
sections of rodent and human material, and found it possible to trace 
to their destination the fibers of the n. intermedius by their histological 
character; that is to say, from the frequency of the sheath nuclei, the 
small size of the fibers, and the presence of scattered ganglion cells lying 
along the course of the fibers. 
The common identity of the pars intermedius geniculate ganglion and 
chorda tympani, as described by Sapolini and Penso, in the adult is less 
easily seen in the early embryo owing to the incomplete differentiation 
of these structures. In fact, His, Jr., 89, states that up to the third 
month no nerve is to be seen arising between facial and acoustic, and 
he concludes that the intermedius must until that time run in the 
trunks of these two nerves. In our embryos, however, it was found 
earlier than that. The Fig. 6 represents the pars intermedius and geni- 
culate ganglion in an embryo of 3} weeks, and- they can also be dis- 
Fic. 8. Sagittal section through the geniculate ganglion and facial nerve 
of a 30 mm. human embryo, No. 75, Mall Collection, showing how they are 
separated by a connective tissue partition. 
tinguished in embryo No. 148, Mall collection, which is about 20 days 
old. The ganglion can be made out first, and shortly after that the 
path of loose fibers connecting it with the neural tube. As is seen in 
Fig. 6, the ganglion and its proximal root are at this early period dis- 
tinctly separate from the acoustic mass, and it is only as the acoustic 
mass increases in size that it could be said to fuse with the geniculate 
ganglion; the existence even here of a real fusion is doubted, for no 
appearance was observed in any of our embryos that could not be ex- 
plained by mere contiguity. The separation existing between these 
ganglia, in the early stages, merits the attention of those who would 
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