THE ELEVENTH OR SPINAL ACCESSORY NERVE. 



Eleventh Pair (Figs. 491, 492). 



The Eleventh or Spinal Accessory Nerve consists of two parts one the acces- 

 sory part to the vagus, and the other the spinal portion. 



The accessory part is the smaller of the two. Its superficial origin is by four 

 or five delicate filaments from the side of the medulla, below the roots of the vagus. 

 Its deep origin may be traced to a nucleus of gray matter in the medulla, just 

 dorsal to the lower third of the olive and dorso-lateral to the hypoglossal 

 nucleus. It passes outward to the jugular foramen, where it joins with the 

 spinal portion, and is connected with the upper ganglion of the vagus by one or 

 two filaments. It then separates from the spinal portion, passes through the 

 foramen, and is continued over but adherent to the surface of the inferior gan- 

 glion, or ganglion of the trunk of the vagus, to be distributed principally to the 

 pharyngeal and superior laryngeal branches of the pneumogastric. Through the 

 pharyngeal branch it probably supplies the muscles of the soft palate (see page 

 425). Some few filaments from it are continued into the trunk of the vagus 

 below the ganglion, to be distributed with the recurrent laryngeal nerve and 

 probably also with the cardiac nerves. 



The spinal portion is firm in texture. Its superficial origin is by several fila- 

 ments from the lateral tract of the cord, as low down as the sixth cervical nerve. 

 Its deep orijin may be traced to the intermedio-lateral tract (lateral horn) of the 

 gray matter of the cord, where it forms a column of cells reaching, above, to the 

 lower end of the nucleus of the accessory part of the nerve. This portion of the 

 nerve ascends between the ligamentum denticulatum and the posterior roots of 

 the spinal nerves, enters the skull through the foramen magnum, and is then 

 directed outward to the jugular foramen, through which it passes, lying in the same 

 sheath as the pneumogastric, but separated from it by a fold of the arachnoid. In the 

 jugular foramen it joins with the accessory portion. At its exit from the jugular 

 foramen it passes backward, either in front of or behind the internal jugular vein, 

 and descends obliquely behind the Digastric and Stylo-hyoid muscles to the upper 

 part of the Sterno-mastoid. It pierces that muscle, and passes obliquely across 

 the occipital triangle, to terminate in the deep surface of the Trapezius. This 

 nerve gives several branches to the Sterno-mastoid during its passage through it, 

 and joins in its substance with branches from the second cervical, which supply 

 the muscle. In the occipital triangle it joins with the second and third cervical 

 nerves and assists in the formation of the cervical plexus. Beneath the Trapezius 

 it joins with the third and fourth cervical nerves to form a sort of plexus, from 

 which fibres are distributed to the muscle. 



Surgical Anatomy. In cases of spasmodic torticollis in which all palliative treatment has 

 failed, division or excision of a portion of the spinal accessory nerve has oeen resorted to. This 

 may be done either along the anterior or posterior border of the Sterno-mastoid muscle. The 

 former operation is performed by making an incision from the apex of the mastoid process, 

 three inches in length, along the anterior border of the Sterno-mastoid muscle. The anterior 

 border of the muscle is defined and pulled backward, so as to stretch the nerve, which is then to 

 be sought for beneath the Digastric muscle, about two inches below the apex of the mastoid 

 process. The other operation consists in making an incision along the posterior border of the 

 muscle, so that the centre of the incision corresponds to the middle of this border of the mus- 

 cle. The superficial structures having been divided and the border of the muscle defined, the 

 nerve is to be sought for as it emerges from the muscle to cross the occipital triangle. When 

 found, it is to be traced upward through the muscle, and a portion of it excised above the point 

 where it gives off its branches to the Sterno-mastoid. In this operation one of the descending 

 branches of the superficial cervical plexus is liable to be mistaken for the nerve. 



Twelfth Pair (Fig. 493). 



The Twelfth or Hypoglossal Nerve is the motor nerve of the tongue. Its 

 superficial origin is by several filaments, from ten to fifteen in number, from the 

 groove between the pyramid and olivary body, in a continuous line with the 

 anterior roots of the spinal nerves. Its deep origin can be traced to a nucleus of 

 gray matter lying under the lower part of the fasciculus teres (trigonum hypo- 



