794 



THE NERVOUS SYSTEM. 



pharyngeal plexus (lingual branch of the vagus) ; and (5) medial to the mylo-hyoid musclt 

 at the anterior border of the hyoglossus, it forms loops of communication with the lingua 

 branch of the mandibular nerve. 



The branches of the nerve are : (1) Eecurrent ; (2) Descending ; (3) Thyreo 

 hyoid ; and (4) Lingual. 



Ramus Recurrens. The recurrent branch passes from the nerve near its origin t 

 supply the dura mater of the posterior fossa of the base of the skull. It probabl 

 derives its fibres from the communication with the first and second cervical nerves 



Ci 



SCENOINC CERVICAL 



FIG. 664. THE MUSCLES OF THE HYOID BONE AND STYLOID PROCESS, AND THE 

 EXTRINSIC MUSCLES OF THE TONGUE, WITH THEIR NERVES. 



Ramus Descendens. The descending branch of the hypoglossal nerve is th< 

 chief branch given off in the neck. It arises from the hypoglossal nerve as i 

 crosses the internal carotid artery, and descends in the anterior triangle superncia 

 to the carotid sheath. It is joined about the middle of the neck by the descendinj 

 cervical nerve (from the second and third cervical nerves). By their union th< 

 ansa hypoglossi (hypoglossal loop) is formed, from which branches are distributed t 

 the majority of the infra-hyoid muscles both bellies of the omo-hyoid, the sterno 

 hyoid, and the sterno-thyreoid. The descending branch of the hypoglossal nervi 

 derives its fibres from the communication to the hypoglossal nerve from the loo] 

 between the first and second cervical nerves ; so that the ansa hypoglossi is madi 

 up of fibres of the first three cervical nerves. 



