194 THE NERVOUS SYSTEM 



3. General Visceral Efferent Fibers. Cells of origin in the dorsal motor nucleus 

 of the vagus. Fibers run to the sympathetic ganglia of the vagal plexuses for 

 the innervation of the thoracic and abdominal viscera. 



4. Special Visceral Efferent Fibers. Cells of origin in the nucleus ambiguus. 

 Termination in the striated musculature of the pharynx and larynx. 



XI. Accessory Nerve. Superficial origin from the posterior lateral sulcus 

 of the medulla oblongata caudal to the ninth and tenth and from the lateral as- 

 pect of the first five or six cervical segments of the spinal cord. Composition 

 (Fig. 120): 



1. General Visceral Efferent Fibers. Cells of origin in the dorsal motor 

 nucleus of the vagus. Fibers run in the bulbar rootlets and then by way of the 

 internal ramus of the accessory to join the vagus, and end in the sympathetic 

 plexuses, associated with the vagus nerve, for the innervation of thoracic and 

 abdominal viscera. 



2. Special Visceral Efferent Fibers. These fall into two groups: A, fibers, 

 whose cells of origin are located in the nucleus ambiguus, and which run by way of 

 the internal ramus of the accessory to join the vagus and are distributed through 

 it to the striated muscles of the pharynx and larynx; B, fibers, whose cells of 

 origin lie in the lateral part of the anterior gray column of the first five or six 

 cervical segments of the spinal cord, and which ascend in the spinal root of the 

 accessory nerve and then run in its external ramus to end in the trapezius and 

 the sternocleidomastoid muscles. 



XII. Hypoglossal Nerve. Superficial origin from the anterior lateral sulcus 

 of the medulla between the pyramid and the olive. It is composed of somatic 

 efferent fibers, whose cells of origin are located in the hypoglossal nucleus and 

 whose termination is in the musculature of the tongue. 



