THE HYPOGLOSSAL NERVE. 



273 



jugular vein, where they are often, joined by filaments from the superior cervical 

 ganglion of the sympathetic (Luschka). 



The descending cervical nerve (r. descendens hypoylossi) consists mainly of 

 fibres which pass to the hypoglossal from the first and second cervical nerves in the 

 communication below the skull. Leaving the trunk as it turns round the occipital 

 artery, or a little higher up, the descending nerve runs downwards on the surface of 

 the common carotid artery, inclining gradually from the outer to the inner side, and 



Fig. 184. PLAN OF THK CONNECTIONS 



OK THE HYPOGLOSSAL WITH THE 

 CERVfCAL NERVES, AND THE FOR- 

 MATION OF THE ANSA CERVICALIS. 



( After Holl.) 



being placed generally within, 

 but sometimes on the front of, 

 the carotid sheath. After 

 having given off a branch to 

 the anterior belly of the omo- 

 hyoid muscle, it joins about 

 the middle of the neck in a 

 loop (ansa cervicalis) with 

 the communicating cervical 

 branches from the second and 

 third cervical nerves. The 

 concavity of the loop is turned 

 upwards, and the connection 

 between the nerves is fre- 

 quently effected by two or 

 more interlacing filaments 

 which form a small plexus. 

 From this interlacement of the 

 nerves, offsets are continued 

 backwards to the posterior 

 belly of the omo-hyoid, and 

 downwards to the sterno-hyoid 

 and sterno-thyroid muscles. 



Muscular branches. 

 The branch to the thyro-hyoid 

 muscle is a separate twig also 

 composed of fibres proceeding 

 from the cervical nerves, and 

 leaving the hypoglossal trunk 

 as it approaches the hyoid bone. 



As it lies beneath the mylo-hyoid, the nerve gives offsets to the styloglossus, hyo- 

 glossus and genio-hyoid muscles, and the terminal branches, penetrating the genio- 

 glossus, supply that muscle and' the intrinsic muscles of the tongue. According to 

 Holl the nerve to the genio-hyoid is of cervical origin. 



The fibres proceeding from the first and second cervical nerves do not become mingled with 

 those of the hypoglossal trunk, but for the most part form a small cord which can be 

 separated from the latter by removing the common sheath, and followed down into the 

 descending 1 cervical nerve. A minute funiculus runs proximally with the hypoglossal nerve, 

 and others pass on the deep aspect of the trunk to the recti antici. The descending cervical nerve 



