Drxon— On the Development of the Branches of the Fifth Cranial Nerve in Man. 65 
connection of the motor root of the fifth nerve with the inferior maxillary division, 
is not at all similar to the connection which exists between the motor and sensory 
roots of a spinal nerve. In the case of the fifth cranial nerve the motor root 
simply crosses the sensory fibres, and at once passes into the muscles of mastica- 
tion; an exchange of fibres between the motor and sensory parts takes place only 
to a very limited extent—“ nur zwei Zweige erfahren einen wirklichen Austausch 
der Bahnen, der mit dem N. mandibularis gehende N. mylohyoideus und der in 
Begleitung der Muskelnerven gehende N. buccinatorius.” Professor His notes 
that there is thus no @ prior? reason why the motor root of the fifth nerve should 
not be counted a distinct cranial nerve as has been suggested by Faesebeck. 
All the important branches of the inferior maxillary nerve are represented in 
the embryo in the beginning of the sixth week (C.R.), just as we have found all 
the branches of the ophthalmic division are. 
The two accessory ganglia of the inferior maxillary nerve (otic and submaxil- 
lary) appear about the same time, the submaxillary possibly a little earlier than 
the otic (see page 58), and no proof was found that their cells are derived directly 
from the cells of the Gasserian ganglion. The connections of these ganglia with 
the inferior maxillary nerve, can in no sense be compared to the connection which 
exists between a spinal ganglion and its posterior nerve root, for the accessory 
ganglia of the inferior maxillary nerve do not appear until after the branches 
with which they are connected, have been formed. These embryological observa- 
tions are in accordance with the results of Von Gustaf Retzius,* who finds, that 
the cells of these ganglia, just as those of the ciliary and the ganglion of Meckel, 
possess the characters of typical sympathetic nerve cells. 
The development of the connections of the trigeminal with the seventh and 
ninth nerves is of great interest. In the above description it will be seen that in 
Rw. (5th week) the chorda typani nerve does not join the lingual (page 58 and 
fig. 15, Plate IL), but that it is connected only with the seventh nerve. The 
chorda tympani is thus developed from, and is a branch of, the seventh nerve. 
Also in this embryo the Vidian nerve (page 51) does not yet communicate with 
the ganglion of Meckel, or superior maxillary nerve; thus the Vidian, or great 
superficial petrosal, must be looked on as a branch of the geniculate ganglion of 
the facial, with which it is seen to be in connection. Professor His has described 
and figured the chorda tympani as arising from the facial in embryo K.O., which 
is a little more than 1 mm. longer than Ru. Further, I may state, that in the 
rat embryo, there is no doubt, that in the first instance both Vidian and chorda 
tympani have no other connections except with the seventh nerve, as in man. 
The nerve of Jacobson in Ru. (5th week) is seen to be an outgrowth of the petrous 
ganglion of the glosso-pharyngeal nerve, and is not yet connected with the trigeminal 
* « Ueber das Ganglion Ciliare,’’ Anatomischer Anzeiger, July, 1894, p. 633. 
