THE SPINAL ACCESSORY NERVE. 635 



Tracheal and cesophageal brandies spring from it as it ascends in the to trachea, 

 neck ; and near the larynx some filaments are furnished to the ^ P EgUS ' 

 inferior constrictor muscle. pharynx. 



On the left si'l- the recurrent nerve arises in the thorax, opposite Left 

 the arch of the aorta ; in the neck it lies between the trachea and 

 oesophagus, as on the right side, and is more frequently behind the 

 inferior thyroid artery. 



The SPINAL ACCESSORY NERVE courses through the jugular fora- Eleventh 



with the pneumo-gastric, but is not marked by any ganglion. m 

 The nerve is composed of two parts, a smaller one, accessory to has two 

 the vagus, and a larger, spinal part, which have a different origin and pa 

 distribution. 



The part accesswy to the vagus (bulbar part; fig. 226, u ) arises from Accessory 

 the medulla oblongata, and ends by joining the pneumo-gastric out- tovagus 

 side the skull. In the foramen of exit it lies close to the vagus, and 

 ii connected to the upper ganglion of that nerve by one or two 

 filaments. Below the foramen it passes over the lower ganglion of below 

 the vagus, and blends with the trunk beyond that ganglion. It foramen - 

 gives distinct offsets to join the pharyngeal and superior laryngeal 

 branches of the pneumo-gastric ; and other fibres are continued into 

 the cardiac and recurrent laryngeal branches. 



The spinal part (fig. 226, 1 -), which takes its origin from the spinal Spinal part 

 cord, is much larger, and is connected with the smaller piece while m 

 passing through the jugular foramen. Beyond the foramen the nerve in the neck 

 (fig. 225, 2 ) takes a backward course through the sterno-mastoid, and 

 across the side of the neck to end in the tiapezius : at first it is con- crosses to 

 cealed by the jugular vein, but it then passes either over or under ra P ezms > 

 that vessel. The connections of the nerve beyond the sterno-mastoid 

 have been already examined. 



The nerve furnishes muscular offsets to the sterno-mastoid and to supplies 

 ,1 . muscles, 



the trapezius. 



The HYPOGLOSSAL NERVE, issuing from the cranium by the Twelfth 

 anterior condylar foramen, is at first deeply placed between the ne 

 internal carotid artery and the jugular vein (fig. 225, 4 ). It next 

 comes forward between the vein and artery, turning round the 

 outer side of the vagus to which it is closely united. The nerve 

 now descends in the neck, and becomes superficial below the digastric 

 muscle in the anterior triangular space (p. 602) ; from this spot it is 

 directed forwards to the tongue and its muscles (p. 625). 



Connecting brandies. Near the skull the hypoglossal is united to branches 

 the lower ganglion of the vagus by filaments crossing between the ^gus, 

 two nerves as they are in contact. 



A little lower clown the nerve is joined by offsets from the sympa- 

 sympathetic and the loop of the first two spinal nerves. spfnai' m 



The brandies for distribution have been met with in the foregoing lierve - s> and 

 dissections. Thus, in the neck its descending branch supplies, in muscles, 

 common with the spinal nerves, the depressors of the hyoid bone. 

 In the submaxillary region it furnishes branches to one elevator 

 (genio-hyoid) of the hyoid bone, to the extrinsic muscles of the 



