Dixon—On the Development of the Branches of the Fifth Cranial Nerve in Man. 638 
following manner * :—A fine twig, which represents the nerve of Jacobson, passes 
upwards from the petrous ganglion of the glosso-pharyngeal nerve into the interval 
between the Eustachian tube and the periotic capsule. This fine nerve lies at its 
origin in Wt., at least 0°3 mm., and in F’.M., 0:25 mm. to the outer side of the 
carotid artery, which also ascends in this interval. As the artery and nerve 
ascend, the artery bends outwards towards the nerve. The nerve now divides into 
two branches, one of which runs on the outer side of the artery and joins the 
Vidian, as the latter nerve crosses the artery, while the other branch ends in the 
posterior and lower part of the otic ganglion, and therefore represents the small 
superficial petrosal nerve, of the adult. In addition to this nerve of Jacobson, 
which lies on the outer side of the carotid artery, there is a fine nerve present on 
the inner side of the carotid. This last nerve is continued along the side of the 
carotid, into the cranium, after it has given a communicating twig to the Vidian 
nerve. When traced in the opposite direction, the nerve on the inner side of the 
carotid, is found to spring chiefly from the trunk ganglion of the vagus nerve. In 
its course it crosses the petrous ganglion of the glosso-pharyngeal, and may receive 
some of its fibres from it. The position and connections of this last described 
nerve render it probable that it represents the ‘“‘ sympathethic,” associated with the 
carotid, in the adult. 
In Embryo Mk. (eighth week) the same branches of the inferior maxillary 
nerve are recognisable as in F’. M., but the large motor branches, are given off 
to the individual muscles, and can now therefore be named. The connections of 
the smaller ganglia of the fifth, are much more easily traced than in the younger 
stages, also the ganglia themselves are very sharply defined. The otic ganglion 
is placed behind, and to the inner side, of the trunk of the inferior maxillary 
nerve. The ganglion is of large size, and from it a process can be traced up 
inside the cranium which comes close to the inner and under surface of the 
Gasserian ganglion. . 
This part of the otic ganglion, which lies inside the cranium, beneath the 
Gasserian ganglion, in C. R., F. M., and Mr. (and also in embryo Wt. about the 
same age as I’. M.), probably represents the ganglionic mass, described by Ewart, 
in a five months embryo, as the ganglion of the ramus profundus branch of the 
ophthalmic nerve. In these embryos, it has however, no connection with the 
ophthalmic nerve. 
In Mr., the connections of the ganglia of the fifth nerve with the petrous 
ganglion of the ninth, are practically similar to those described and figured for 
F.M. The nerve of Jacobson comes from the outer and upper part of the petrous 
ganglion of the glosso-pharyngeal, and passes upwards between the Eustachian 
*See fig. 10, Plate I. 
