George L. Streeter 163 
believe that they have a common origin, as was thought by the younger 
His. 
In Fig. 6 the ventral or motor division of the facial nerve can be 
seen cut obliquely at the ventral edge of the geniculate ganglion. In 
this embryo the dorsal root or pars intermedius is fully as large as the 
ventral or motor root; but the proportion is gradually reversed as one 
looks through older stages, due to the more rapid growth of the ventral 
root. The pars intermedius is in this sense a more prominent structure 
in foetal life than in the adult, indicating that phylogenetically it has 
played a more important role in lower forms than in man. With the 
development of the connective tissue the geniculate ganglion becomes 
inclosed in a sheath, and is walled off from the motor root, against which 
it continues to lie, as may be seen in Fig. 8. In this figure the ganglion 
is cut somewhat obliquely, and at the two ends can be seen the central 
and peripheral fibers of the ganglion. To determine the destination of 
the peripheral fibers dissections were made of embryonic pigs and it 
was found easy to demonstrate in 3-20 cm. embryos that the distal fibers 
leave at one corner of the ganglion by the great superficial petrosal nerve 
and at the other by a bundle that runs along the motor division until it 
leaves it as the chorda tympani. Fig. 7 represents such a dissection 
made in a 20 em. pig, showing the nature of the anastomosis with the 
auricular branch of the vagus, and following essentially the arrangement 
described by Sapolini and Penso. 
In these dissections of the seventh nerve of pig embryos a ganglion 
cell mass, connected with the pons ganglia, was seen extending caudal- 
wards as a surface ridge which could be traced beginning at the fifth 
nerve and then passing in between the seventh and eighth nerves and 
finally ending on the dorso-lateral surface of the restiform body. This 
is apparently the same structure that has been found by Mr. C. R. Essick, 
of the Johns Hopkins Medical School, in human adult material, and 
a full description of which he has now ready for publication. 
REFERENCES. 
ALEXANDER, G., g9.—Zur Anatomie des Ganglion vestibulare der Saugethiere. 
Sitz. d. Kais. Akad. d. Wiss., math.-naturw. Classe, Bd. 108, Abth. 
III, 1899. 
o1.—Zur Entwicklung des Ductus endolymphaticus. Arch. f. Ohren- 
heilkunde, Bd. 52. 
BOrTcHER, A., 69.—Ueber Entwick. u. Bau des Gehorlabyrinthes. Verhandl. 
d. Kaiserl. Leop. Carol. deutschen Akad. der Naturforscher., Bd. 35. 
