This nerve arises from the outer edge of the medulla oblongata, and passes from the cranium through the back part of the foramen lacerum basis cranii. At this point it has upon it Andersen's ganglion, from which the nerve of Jacobson is derived.

It now descends behind the great cornu of the hyoid bone to reach the base of the tongue, where it supplies filaments to the mucous membrane and sends others to the muscles of the pharynx.

Branches given off in its course: - A very fine filament (Jacobson's nerve), which enters a small foramen in the petrous portion of the temporal bone to be distributed to the tympanum.

Two or three filaments to the superior cervical ganglion.

A branch which, with some sympathetic filaments, go to the common carotid.

A pharyngeal branch. This passes to the upper wall of the pharynx, and, with the pharyngeal filaments of the pneumogastric and sympathetic nerves, forms a somewhat intricate plexus.