454 HYPOGLOSSAL NERVE. 



then passes obliquely across the neck, communicating with the second, 

 third, and fourth cervical nerves, and is distributed to the trapezius. 

 The spinal accessory sends numerous twigs to the sterno-mastoid in its 

 passage through that muscle, and in the trapezius the nervous filaments 

 may be traced downwards to its lower border. 



The pneumogastric and spinal accessory nerves together (nervus 

 vagus cum accessorio) resemble a spinal nerve, of which the former 

 with its ganglion is the posterior and sensitive root, the latter the an- 

 terior and motor root. 



NINTH PAIR.* HYPOGLOSSAL NERVE (lingual). The hypoglos- 

 sal nerve arises from the groove between the corpus pyramidale and 

 corpus olivare by ten or fifteen filaments, which being collected into 

 two bundles, escape from the cranium through the anterior condyloid 

 foramen. The nerve then passes forwards between the internal 

 carotid artery and internal jugular vein, and descends along the 

 anterior and inner side of the vein to a point parallel with the angle 

 of the lower jaw. It next curves inwards around the occipital artery, 

 with which it forms a loop, and crossing the lower part of the hyo- 

 glossus muscle to the genio-hyo-glossus, sends filaments onwards with 

 the anterior fibres of that muscle as far as the tip of the tongue. 

 It is distributed to the muscles of the tongue, and principally to the 

 genio-hyo-glossus. While resting on the hyo-glossus muscle it is 

 flattened, and beneath the mylo-hyoideus it communicates with the 

 gustatory nerve. 



At its origin the hypoglossal nerve sometimes communicates with 

 the posterior root of the first cervical nerve. 



The Branches of the hypoglossal nerve are : 



Communicating branches with the Pneumogastric, 

 Spinal accessory, 

 First and second cervical nerves, 

 Sympathetic. 



Descendens noni, 



Thyro-hyoidean branch, 



Communicating filaments with the gustatory nerve. 



The Communications with the pneumogastric and spinal accessory 

 take place through the medium of a plexiform interlacement of branches 

 at the base of the skull, behind the internal jugular vein. The com- 

 munications with the sympathetic nerve are derived from the superior 

 cervical ganglion. 



The Descendens noni is a long and slender twig, which quits the 

 hypoglossal just as that nerve is about to form its arch around the 

 occipital artery, and descends upon the sheath of the carotid vessels. 

 Just below the middle of the neck it forms a loop with a long branch 



* The twelfth pair according to the arrangement of Soemmering. 



