628 



NERVOUS SYSTEM. 



upper two cervical nerves. These filaments, however, are not constant. It frequently, 

 though not constantly, sends a few filaments to the superior ganglion, or the ganglion of 

 the root of the pneumogastric. After it has emerged by the jugular foramen, it sends a 

 branch of considerable size to the pneumogastric, from which nerve it also receives a few 

 filaments of communication. This branch will be again referred to in connection with 

 the distribution of the nerve. In its course, it also receives filaments of communication 

 from the anterior branches of the second, third, and fourth cervical nerves. 



In its distribution, the spinal accessory presents two branches. The first, or anasto- 

 motic branch, passes to the pneumogastric just below the plexiform enlargement which 

 is sometimes called the ganglion of the trunk of the pneumogastric. 



The internal, or anastomotic branch, is composed principally, if not entirely, of the 

 filaments that take their origin from the medulla oblongata. As it joins the pneumogas- 

 tric, it subdivides into two smaller branches. The first of these forms a portion of the 



pharyngeal branch of the pneumogastric. The 

 second becomes intimately united with the 

 pneumogastric, lying at its posterior portion, 

 and furnishes filaments to the inferior, or re- 

 current laryngeal branch, which is distributed 

 to all of the muscles of the larynx except the 

 crico-thyroid. The passage of the filaments 

 from the spinal accessory to the pharyngeal 

 branch of the pneumogastric is easily observed ; 

 but the fact that filaments from this nerve pass 

 to the larynx by the recurrent laryngeal has 

 been ascertained only by physiological experi- 

 ments. 



The external, or large branch of the spinal 

 accessory, called the muscular branch, pene- 

 trates and passes through the posterior portion 

 of the upper third of the sterno-cleido-mastoid 

 muscle, goes to the anterior surface of the trape- 

 zius, which muscle receives its ultimate branches 

 of distribution. In its passage through the 

 sterno-cleido-mastoid, it joins with branches 

 from the second and third cervical nerves and 

 sends filaments of distribution to the muscle. 

 Although the two muscles just mentioned re- 

 ceive numerous motor filaments from the spinal 

 accessory, they are also supplied from the cer- 

 vical nerves ; and, consequently, they are not 

 entirely paralyzed when the spinal accessory is 

 divided. 



FIG. 209. Spinal accessory nerve. (Hirschfeld.) 

 1, trunk of the facial nerve ; 2. 2, glosso-pharyngeal 

 nerve; 3, 3, pneumogastric; 4, 4, 4, trunk, of 

 the spinal accessory ; 5, sublingual nerve ; '6, 

 superior cervical ganglion ; T. T. anastomosis of 

 the first two cervical nerves ; 8. carotid branch of 

 the sympathetic; 9, 10, 11, 12, 13, branches of the 

 glosso-pharyngeal ; 14, 15, branches of the fa- 

 cial; 16, otic ganglion; 17, auricular branch of 

 the pneumogastric; 18, anastomosing branch 

 from the spinal accessory to the pneumogas- 

 tric; 19, anastomosis of the first pair of cervical 

 nerves with the sublingual ; 20, anastomosis of 



Properties and Functions of the Spinal Ac- 

 cessory. Notwithstanding the great difficulty in 

 exposing and in operating upon the roots of the 

 spinal accessory, it has been demonstrated that 

 their galvanization produces convulsive move- 

 ments in certain muscles. The most satisfactory 

 experiments with relation to the general proper- 

 ties of the roots were made by Bernard. This physiologist cut through the occipito- 

 atloid membranes and galvanized the filaments within the spinal canal. By galvanizing 

 the filaments arising from the medulla oblongata, he produced contractions of the mus- 



superior laryngeal nerve ; 23, external laryngeal 

 nerve ; 24, middle cervical ganglion. 



