NINTH PAIR OF NERVES. 505 



It arises by small filaments, which come off from the spinal 

 marrow, between the anterior and posterior fasciculi of the 

 cervical nerves, and proceeds upwards to the great occipital 

 foramen, between these fasciculi. It commences sometimes 

 at the sixth or seventh cervical vertebra, and sometimes about 

 the fourth. It enters the cavity of the cranium through the 

 foramen magnum, and proceeds upwards and outwards, so as to 

 join the eighth pair of nerves at some distance from its origin, and 

 in this course it receives filaments from the medulla oblongata. 



After approaching very near to the eighth pair of nerves, 

 it accompanies it to the foramen lacerum, and passes out in 

 its own separate sheath. It then leaves the eighth pair and 

 descends towards the shoulder, proceeding through the sterno- 

 mastoid muscle. Soon after it emerges from the cranium, it 

 sends a ramification to the pharyngeal branch of the Par 

 Vagum and another to the Par Vagum itself. After passing 

 through the upper and back part of the sterno-mastoid muscle 

 it terminates in the trapezius. It adheres to the ninth pair of 

 nerves as it passes by it, and sends a twig to the sub-occipital 

 and some of the cervical nerves. It also gives ramifications to 

 the sterno-mastoid muscle as it passes through it. 



It has already been stated that the Laryngeal and Recurrent Nerves appear to 

 answer different purposes in their distribution to the Larynx. When both of 

 the recurrent nerves are divided in a living animal, the voice seems to be 

 lost. When the laryngeal nerves only are divided, the strength of the voice 

 remains, but it is flatter. The recurrent nerves, therefore, seem essential 

 to the formation of the voice. The laryngeal nerves are necessary to its 

 modulation. 



The history of the investigation of this subject up to that time, is contained in 

 Mr. Haighton's paper in the third volume of Memoirs of the Medical Society 

 of London. The later researches of Mr. Reid and Mr. Hilton, may be 

 studied with advantage in regard to the structure and functions of the par 

 vagum nerves. 



The Ninth Pair of Nerves. 



Each of these nerves arises from the groove in the medulla 



pharnygeal branch forming the pharyngeal plexus (14), assisted by a branch 

 from the glosso-pharyngeal (8), and one from the superior laryngeal nerve (15). 

 16. Cardiac branches. 17. Recurrent larvngeal branch. 18. Anterior pulmo- 

 nary branches. 19. Posterior pulmonary branches. 20. (Esophageal plexus. 

 21. Gastric branches. 22. Origin of the spinal accessory nerve. 23. Its 

 branches distributed to the sterno-mastoid muscle. 24. Its branches to the 

 trapezius muscle. 



VOL. II. 43 



