, ne | THE TWELFTH OR HYPOGLOSSAL NERVE. 
; 655 
nerves, on the outer side of the internal carotid artery; it then curves forwards 
and downwards over the two carotid arteries lying beneath the digastric and 
stylo-hyoid muscles. As it crosses the external carotid artery it hooks round the 
occipital artery. Above the great cornu of the hyoid bone the nerve conceals 
HyYpoGhossaAL NERVE VAGUS NERVE 
RECURRENT BRANCH | Superior cervical ganglion of the sympathetic 
\) i 
First CERVICAL NERVE 
SECOND CERVICAL NERVE 
Styloglossus 
| Stylohyoid ligament 
| Stylohyoid 
} 
GLosso-PHARYNGEAL 
NERVES 
THIRD CERVICAL NERVE \ 
Keger 
Stylophary1 
Superior constrictor 
| LINGUAL NERVE 
a, Genio-hyoglossus 
PHARYNGEAL BRANCH OF VACUS— 
Digastric —— 
DESCENDENS HYPOGLOSSI 
Middle constrictor —— Digastric 
> ; th Genio-hyoid 
]) ( - 
| 
~—Mylo-hyoid (cut) 
Wy IK 
if 
if f fj 
~Thyro-hyoid 
INTERNAL LARYNGEAL NERVE~ j — Sterno-hyoid 
ANSA HYPOGLOSSI~ 
Inferior constrictor~ —Omo-hyoid 
Sterno-thyroid 
Omo-hyoid 
Fic. 471.—TuHe Muscies OF THE Hyotp BONE AND STYLOID PROCESS, AND THE EXTRINSIC MUSCLES OF 
THE TONGUE, WITH THEIR NERVES. 
the lingual artery; and it then disappears between the mylo-hyoid and hyo-glossus 
muscles to reach the tongue, in the muscular substance of which it terminates. 
Communications.—In its course the hypoglossal nerve has the following communica- 
tions with other nerves :—Near the base of the skull it is connected by small branches 
with (1) the superior cervical ganglion of the sympathetic; (2) the ganglion of the 
trunk of the pneumogastric; (3) by a larger branch, with the loop between the first 
two cervical nerves ; (4) as it crosses the external carotid artery it receives a communica- 
tion from the pharyngeal plexus (lingual branch of the vagus); and (5) beneath the mylo- 
hyoid muscle, at the anterior border of the hyo-glossus, it forms loops of communication 
with the lingual branch of the inferior maxillary nerve. 
The branches of the nerve are:—(1) Recurrent; (2) Descending; (5) Thyro- 
hyoid; and (4) Lingual. 
The recurrent branch passes from the nerve near its origin to supply the dura 
Ss 
