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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
it again. As its exit from the jugular foramen, it runs backward in front of the internal jugular vein in 66.6 per cent. of cases, and behind in it 33.3 per cent. (Tandler). The nerve then descends obliquely behind the Digastricus and Stylohyoideus to the upper part of the Sternocleidomastoideus; it pierces this muscle, and courses obliquely across the posterior triangle of the neck, to end in the deep surface of the Trapezius. As it traverses the Sternocleidomastoideus it gives several filaments to the muscle, and joins with branches from the second cervical nerve. In the posterior triangle it unites with the second and third cervical nerves, while beneath the Trapezius it forms a plexus with the third and fourth cervical nerves, and from this plexus fibers are distributed to the muscle.


FIG. 794– Hypoglossal nerve, cervical plexus, and their branches. (See enlarged image)

 
5l. The Hypoglossal Nerve
 
  
(N. Hypoglossus; Twelfth Nerve)


The hypoglossal nerve (Figs. 794, 795) is the motor nerve of the tongue.
  Its fibers arise from the cells of the hypoglossal nucleus, which is an upward prolongation of the base of the anterior column of gray substance of the medulla spinalis. This nucleus is about 2 cm. in length, and its upper part corresponds with the trigonum hypoglossi, or lower portion of the medial eminence of the rhomboid fossa (page 779). The lower part of the nucleus extends downward into the closed part of the medulla oblongata, and there lies in relation to the ventro-lateral

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