THE NERVES. 401 



ing on it and its ganglion, and dividing into its two branches. 

 It is a motor nerve, and holds the same relation to the vagus 

 as the posterior root of a spinal nerve does to the anterior. 



1. Ram. int&rnus, passes downwards, partly into the nerv. 

 pharyng. superior, partly through the plex. ganglioform 

 (probably into the laryng. superior, and) into the thorax, to 

 the nerv. recurrens, the pharyngeal and gastric plexus. 



2. Ram. externus, the posterior branch, the continuation of the 

 trunk, descends behind ven. jugular, interna outwards and 

 backwards, perforates m. sternockidomast. at the superior 

 third, gives branches to it, becomes enlarged by means of 

 branches from the second and third cervical nerves, and 

 enters the m. trapezius on the internal surface, ramifying in it 

 as far downwards as its inferior extremity. 



648. XII. Nerv. Hypoglossus, the lingual Nerve. 



Origin : between corp. pyramidale and olivare, with ten to fif- 

 teen filaments, which unite into two fasciculi, in a row with the 

 anterior roots of the spinal nerves, behind the art. vertebralis. 

 Course : the two fasciculi, covered by the pia mater, perforate the 

 dura mater separately, become covered by it, and ascend to the 

 foram. condyloid. anterius, through which the united trunk passes 

 out of the cranial cavity (one line thick). Hence it passes down- 

 wards and forwards, situated internal to and behind n. accessorius, 

 vagus, and v.jugularis interna ; inclining in a curve from above, 

 behind and internally over vagus and carotis (over the place of 

 bifurcation) forwards, upwards, and inwards, to the tongue. Here 

 it is situated, at first, internal to and under m. digastricus, then, 

 above art. thyreoid. and lingualis, external to them, internal to 

 m. stylo-glossus. Finally, it passes upwards and forwards into 

 the flesh at the inferior surface of the tongue, covered by gland, 

 submaxillaris and m. mylo-hyoideus, where it terminates at the 

 apex. 



Connecting branches with : the first cervical ganglion of the 

 sympathetic, and the first and second cervical nerves, n. vagus, 

 n. lingualis trigemini. Vascular branches : to carotis andjugu- 

 laris interna and art. lingualis. Muscular branches for : hyo- 

 thyreoid., genio-hyoideus, hyo-, stylo-, genio-glossus, and gland, 

 submaxillaris. Finally : 



Ram. descend, hypoglossi, arises from the commencement of 



the curve, descends outside the carotis before the vagus (in 



the same sheath), anastomoses with it, the third cervical 



nerves [sometimes the second or even the fourth], gives 



26 



