88 A MANUAL OF ANATOMY. 



Divide the mylohyoid along the median raphe and at its insertion into the 

 hyoid bone, and reflect the several parts of the muscles. 



The Hypoglossal Nerve. Figs. 10, 16, 17, 18. 



The hypoglossal nerve leaves the skull through the ante- 

 rior condyloid foramen, winds outward around the ganglion 

 of the trunk of the pneumogastric nerve from behind forward, 

 passes between the internal jugular vein and the internal caro- 

 tid artery, appears at the lower border of the digastric, 

 turns forward around the occipital artery and across the 

 internal and external carotids, and extends into the muscles 

 of the tongue (resting upon the hyoglossus and under 

 the mylohyoid), where it breaks up into its terminal 

 branches. 



For the part that the nerve takes in forming the lingual 

 triangle, see page 85. 



As the hypoglossal nerve crosses the ganglion of the 

 pneumogastric, it receives filaments from that nerve, the 

 sympathetic, and a branch from the first and second cervi- 

 cal nerves. See Cervical Plexus, page 89. 



Branches. The descendens hypog-lossi. This is com- 

 posed of the fibres derived from the cervical plexus (first 

 and second). It leaves the hypoglossal nerve' as it is turn- 

 ing around the occipital artery (may come off much higher) 

 and runs forward and downward upon the sheath of the 

 carotid, where it is joined (in the middle of the neck) by the 

 communicantes hypoglossi, forming the ansa hypoglossi 

 (hypoglossal loop). 



The descendens hypoglossi gives off a small branch to 

 the anterior belly of the omohyoid muscle before the for- 

 mation of the loop. From the loop branches are supplied 

 to the posterior belly of the omohyoid, the sternohyoid, 

 and sternothyroid muscles. 



The hypoglossal also gives off a small branch just below 



