THE NERVES. 405 



with an anterior branch, going through the parotis as far as 

 the angle of the mouth, and unites with nerv.facialis,\vlth 

 a posterior branch directly upwards to the skin on the ante- 

 rior part of the auricle. The central unites with the last, 

 giving branches upwards to the chin, downwards to the 

 inferior region of the neck ; the inferior inclines before the 

 ven. jugular, externa inwards, sends branches to the most 

 inferior region of the cervical skin, and on the chest, 

 b. Ramus posterior, contributes to the posterior loop, passes 

 under proc. spin, of the second vertebra and into the skin of 

 the centre of the nape of the neck. Branches to : m. trachelo- 

 mastoid., transversal., complexus, splenius capit., semi-spinal, 

 cervic. and trapezius. 



654. 4. 2V". cervicalis IV., 



passes out through the third intervertebral foramen, between the 

 third and fourth cervical vertebra?, gives branches to art. vertebralis, 

 and divides into : 



a. Ram. ant., giving branches to m. rectus capit. antic, major, 

 longus coUi, scakn. med., levat. scapul., to the third and fifth 

 loops. From the last : 



1. Nn. supraclaviculares, for the most part cutaneous nerves, 

 which radiate in the inferior trigonum cervicale between m. 

 sterno-ckido-mast., trapezius and clavicle ; the anterior to 

 the clavicle and mammary gland, the central to the axilla, 

 the posterior to the scapula. 



2. Nerv. phrenicus respiratorius internus (Ch. Bell), the 

 diaphragmatic nerve, arises from the fourth cervical nerve, 

 and is strengthened by filaments from the third, fifth, and 

 sixth, even from the second and seventh ; it unites with the 

 superior cervical ganglion, sometimes with hypoglossus and 

 vagus. Course : before m. scalenus anticus, downwards 

 and inwards, and between art. and v. subclavia into the 

 cavum mediast. antic, of the thorax. It is, here, between 

 Pleura and Pericardium, before the roots of the lungs, 

 without distributing any branches ; on the left side it passes 

 round the apex of the heart (therefore longer). It divides 

 into two principal branches, which radiate upon the superior 

 surface of the diaphragm, and partly pass to its inferior 

 surface, where they anastomose with the plexus phrenicus 

 sijmpathici. It is a mixed nerve, and gives rise, by its 

 motor filaments, to the involuntary respiratory movements 

 of the diaphragm, the two anterior thirds of which it 

 supplies. 



