58 Drxon——On the Development of the Branches of the Fifth Cranial Nerve in Man. 
Empryo Rv. (5th week, 9°1mm.). Figure 15, Plate II. 
The inferior maxillary nerve arises from the lower part of the Gasserian 
ganglion, and into it can be traced the motor root of the trigeminal. The 
fibres of the motor root cross the sensory ones, and are present chiefly in the 
outer part of the inferior maxillary nerve. The nerve at its origin is relatively 
very thick, and is directed downwards and forwards, coming to lie on the outer 
aspect, of the upper end of Meckel’s cartilage. The nerve now becomes much 
more slender, and turning somewhat inwards lies in front rather than on the outer 
side of Meckel’s cartilage. Before the nerve thus changes its direction it gives off 
a very fine branch which passes behind, and to the inner side of the cartilage, and 
probably, as we shall see by a comparison with the next embryo, represents the 
communicating branch to the future lingual nerve.* Among the fibres of the in- 
ferior maxillary nerve near its origin are many nuclei, but no isolated otic 
ganglion was observed. : 
At a lower level than the small branch just noted, and like it, placed behind 
the inner side of Meckel’s cartilage, is the terminal portion of the chorda tym- 
pani branch of the facial nerve. The tissue in which the chorda tympani, and 
perhaps also the small branch of the inferior maxillary nerve ends, has not 
quite the same appearance as the cellular tissue round about. Where these 
nerves end the nuclei close at hand are large, and a few scattered fibres are 
seen among them. This differentiated tissue may possibly represent the develop- 
ing sub-maxillary ganglion. It is to be noted, that the chorda tympani nerve, 
is much larger than the other nerve, and further it is more closely connected 
with this differentiated tissue. This arrangement of these nerves was traced 
on both sides, and corresponded exactly. The main trunk of the inferior 
maxillary nerve, continued along the outer side of Meckel’s cartilage, repre- 
sents the inferior dental nerve. No distinct otic ganglion was found connected 
with the inferior maxillary nerve, in this embryo. The nerve of Jacobson is 
present in this embryo, as an outgrowth from the petrous ganglion of the 
glosso-pharyngeal, but is very short. This nerve passes vertically upwards, and 
ends a considerable distance below the level of the inferior maxillary nerve. 
Ru.—Inferior maxillary nerve to origin of connecting branch = 0-6 mm. 
Inferior maxillary nerve to termination of inferior dental = 1:2 mm. 
Empryo C. R._(beginning of 6th week, 13°6mm.). Figures 16 & 17, Plate II. 
The inferior maxillary nerve arises from the front and lower end of the 
Gasserian ganglion, and is the largest of the three branches of the fifth nerve. 
* Compare figures 15 and 16, Plate II. 
