The hypoglossal nerve runs forwards between the submandibular gland and the hypoglossus well below the lingual nerve. As it crosses the hypoglossus, fibers radiate to supply the extrinsic muscles of the tongue; at the anterior border of the hypoglossus, it plunges into the tongue to supply the intrinsic muscles.
Source: Boileau Grant JC. A Method of Anatomy: Descriptive and Deductive. 5th ed. Baltimore, Md: Williams & Wilkins Co; 1952:754.
April 2004. Arch Surg. 2004;139(4):370. doi:10.1001/archsurg.139.4.370