174 



ANATOMY AND PHYSIOLOGY OF 



within the superior mediastinum ; the right 

 nerve adheres to the trachea, crosses above 

 the root of the right lung, alongside of the 

 esophagus, and gains the under side of 

 that tube before it leaves the chest. On iho 

 left side the nerve accompanies the anterior 

 aorta, and crosses the root of the posterior 

 aorta, and also reaches the esophagus. Its 

 branches within the chest are filaments to 

 the tracheal and cardiac plexuses ; also, a 

 branch called the recurrent nerve ; branches 

 to the pulmonary plexus, and also two 

 cords that branch out and penetrate the 

 walls of the auricles. The recurrent nerve 

 of the left side originates from the par 

 vagum, by the side of the anterior aorta, 

 and coils round the root of the posterior 

 aorta. 



The recurrent nerve, so denominated from 

 its retrograde course, passes upwardly and 

 outwardly, and is found between the caro- 

 tid artery and the trachea ; having reached 

 the top of the latter, it spreads into fine ter- 

 minating branches, several of which run to 

 the muscles of the larynx and thyroid carti- 

 lage, and end in ramifications upon the 

 membrane of the glottis. Its branches are 

 filaments to the pulmonary plexus, cardiac 

 plexus, posterior cervical ganglion, and 

 branches to the esophagus and trachea. 



The par vagum runs to the stomach. 

 The left nerve sends filaments to the heart, 

 and others along the small curvature, which 

 communicates with the ramifications of the 

 right nerve ; the other crosses to the left 

 side, and joins the great semilunar ganglion. 

 The right nerve, as soon as it reaches the 

 heart, divides into numerous branches, 

 which join the left, and spread their ramifi- 

 cations upon the under part of the heart ; 

 some run to the pylorus, and others join the 

 hepatic plexus. 



Accessory nerves to the eightli. — These 

 nerves are considered as accessory to the 

 eighth, in consequence of their being found 

 in close connection in issuing from the 

 cranium ; it originates in the vertebral canal, 

 by the union of several filaments. In its 

 course into the cranium it receives many 

 other fine threads, and in that cavity joins 



the par vagum. Beneath the atlas, the 

 accessory nerve divides ; the front division 

 runs downward, and penetrates the belly, 

 transmitting side twigs in its course. The 

 posterior division turns round the transverse 

 process of the atlas to the scapula, near 

 which it is lost in muscular substance. 

 The branches of the accessory pass to the 

 par vagum, anterior cervical ganglion, and 

 communicate with the sub-occipital nerve. 



Ninth pair, or Unguales, arise behind the 

 eighth pair, from the corpora olivaria ; it is 

 found in company with the par vagum, near 

 the coronoid process. The nerve passes 

 down the lower jaw, between the muscles* 

 forming the root of the tongue, and ends in 

 the tip of the latter. It sends branches to 

 the lingual muscles and to the hyo-glossus 

 longus. 



Tenth pair, or sub-occipital nerves. — They 

 arise from the medulla oblongata, and be- 

 ginning of the spinal marrow; they pass 

 out through a hole in the fore part of the 

 body of the atlas. It then branches into a 

 superior and inferior division. The superior 

 is distributed to the extensor muscles of the 

 head and neck. The inferior branch goes 

 to the trachea, lymphatic glands, and mus- 

 cles of the neck. 



CERVICAL NERVES. 



These consist of seven pairs, originating 

 from the cervical portion of the spinal mar- 

 row. Each nerve, as soon as it issues from 

 the spinal canal, forms two ner\^ous fila- 

 ments, one superior, the other inferior. 



The first cervical nerve makes its exit be- 

 tween the first and second cervical vertebra). 

 It sends branches to difierent muscles, and 

 communicates wdth the 



Second cervical nerve, which makes its 

 appearance between the second and third 

 vertebrae. Its superior filament sends 

 branches to the muscles of the neck, and 

 levator humeri, communicates -with the ac- 

 cessory nerve, and 



Third cervical. — This also sends branches 

 and twigs to the difierent muscles of the 

 neck, and communicates with the fourth. 



The fourth, fifth, sixth, and seventh pairs 



