1276 



HUMAN ANATOMY. 



medulla. The cortico-nuclear fibres then bend dorso-medially and, for the most part but _ 

 not entirely, cross the raphe to enter the ventro-lateral surface of the hypoglossal nucleus of 

 the opposite side and end in arborizations around the root-cells. 



Course and Distribution. — The hypoglossal takes its superficial origin 

 from the surface of the brain-stem in the form of from ten to fifteen slender fasciculi, 

 which emerge from the ventral surface of the medulla in the groove between the 

 olivary eminence and the pyramid (Fig. 1046). 



Fig. 1082. 



.-^i^- 



Digastric muscle, cut 



I. cervical nerve — ^^ 

 Spinal accessory nerve 

 Small occipital nerve 



II. cervical ner\'e 



Hypoglossal nerve 



Superior cervical ganglion. 



Branch of II. cervical to spinal accessory 



III. cervical nerve 



Communicans hypoglossi 



Stumps of great auricular and superficial 



cervical nervesj jy. cervical nerve- 



V, cervical nerve 

 Branch to rhomboide 



VI. cervical nerve 



Branch of communication to 



spinal accessory 



Cutaneous branch 



VII. cervical nerve 



Nerveto subclavius /Jt': 



VIII. cervical 



Posterior thoracic 

 nerve 

 Suprascapular _ 

 nerve 



./ 



4' 



I. thoracic nerve 



External pterygoid muscle. 

 Lingual branch of V. nerve 



\ Chorda t3'mpani nerve 

 -Internal pterygoid muscle 

 Edge of oral mucous membrane 

 Glosso-pharyngeal nerve 

 Mental nerve 

 Inferior dental nerve, cut 

 Sublingual gland 

 Submaxillary ganglion 



Stylo-hyoid muscle 



Thyro-hyoidbranchof XII. nerve 

 Superior laryngeal nerve 



Descendens hypoglossi ; sympathetic 



cord is to its outer side 



\'agus nerve 



External laryngeal nerve 



(Dmo-hyoid muscle, cut 

 Phrenic nerve 



Middle cervical ganglion of sympathetic 

 — Scalenus anticus muscle 



— Subclavian artery 



Deep dissection of neck showing branches of vagus, spinal accessory and hypoglossal nerves. 



These root-bundles pass outward, dorsal to the vertebral artery, and assemble 

 into two groups, which pierce the dura mater separately at a point opposite the 

 anterior condyloid foramen. Either within this canal or as they lea\'e the 

 cranium through its external opening they unite into a single trunk. Arriving at 

 the inferior aspect of the base of the skull, the deeply placed hypoglossal nerve 

 descends and hooks around the' ganglion of the trunk of the vagus, to which it is 

 closely attached by connective tissue. It then takes a downward and forward 

 course between the internal carotid artery and the internal jugular vein. Arriving 

 at the inferior margin of the posterior belly of the digastric, the nerve winds around 

 the occipital artery and courses downward and forward to the outer side of the 

 external and internal carotid arteries. It then continues forward above the hyoid 

 bone to the under surface of the tongue, passing beneath the tendon of the digastric, 



