64 Dixon—On the Development of the Branches of the Fifth Cranial Nerve in Man. 
tube, and the periotic capsule, lying a considerable distance to the outer side of 
the carotid artery. As the nerve passes upwards and forwards, it has connected 
with it several small aggregations of cells with large nuclei. The nerve divides 
into two branches, one of which passes inwards, and having communicated with 
the nerves round the carotid, joms the Vidian. The other branch of the nerve of 
Jacobson passes near the geniculate ganglion of the facial, and finally ends in the 
otic ganglion. 
The carotid artery in this embryo is surrounded by a regular sheath of nerve 
fibres, which can for the most part be traced from the trunk ganglion of the tenth 
nerve, a few, however, also coming from the petrous ganglion of the glosso- 
pharyngeal. 
The above observations on the inferior maxillary nerve show that at first the 
nerve is unbranched, and that the inferior dental nerve of the adult is to be looked 
on as the direct continuation of the first formed inferior maxillary division of the 
fifth nerve, just as the nasal nerve is the continuation of the first formed part of 
the ophthalmic division. I was at first inclined to conclude, that the short nerve 
in embryo Ru. (5th week), which takes origin from the inferior maxillary trunk, 
and passes behind Meckel’s cartilage, represents the lingual nerve of the adult. 
Since, however, the point of origin of this nerve lies nearly 0°6 mm. from the 
place where the motor root crosses the sensory fibres of the inferior maxillary, I 
believe this small nerve cannot represent the lingual of the adult, but rather, the 
communication, which exists in the adult, between the inferior dental and lingual 
nerves. In embryo C.R., an older stage than Rv., the distance of the point of 
origin of the lingual nerve from the crossing point of the motor fibres, is only 
about 0°2 mm., but on the other hand the connecting branch between the inferior 
dental and lingual nerves corresponds very accurately in position to the small 
nerve seen in the Ru. Further, the lingual nerve when recognisable comes off 
the inferior maxillary at a much more acute angle than the small nerve in Ru. 
does. <A reference to figures 15 and 16, Plate II., will, I think, make this point 
clear. The lingual nerve thus resembles the frontal in arising at a comparatively 
late period, and then growing so rapidly as to soon overtake in length the other 
earlier formed nerve. In the rat as in man I have found that the lingual nerve 
is formed late, and is for some time even shorter than the chorda tympani branch 
of the facial nerve. 
From the start the greater part of the motor root of the fifth nerve crosses over 
the sensory fibres of the inferior maxillary division, and takes up a position in the 
outer part of the nerve. Writing on this point, Professor His* remarks that the 
* «Die morphologische Betrachtung der Kopfnerven,” Archiv fiir Anatomie und Physiologie. Anat. 
Abth., 1887, p. 420. 
