514 NERVES OF THE NECK. 



at first three roots, which again divide and unite in a 

 variety of ways to constitute this plexus. Its lower part 

 receives the name of axillary plexus. This plexus commu- 

 nicates with the cervical by means of a filament from the 

 fourth cervical nerve. In the neck it passes between the 

 scalenus anticus and medius muscles, above and outside 

 of the subclavian artery, under the clavicle and sub-cla- 

 vian muscle, over ' the first rib to the axilla, where the 

 branches of this plexus so interlace as completely to sur- 

 round the axillary artery from the clavicle to the head of 

 the humerus. 



The brachial plexus is very extensive, and sends branches 

 to the neck, the anterior part of the chest, and the upper ex- 

 tremity. Only those going to the neck claim our attention 

 in this place. The balance of this plexus will be consid- 

 ered in its appropriate relations with the organs of the 

 chest and superior extremity. 



The branches supplying the neck are termed supra clavic- 

 ular, and go to the subclavian muscle, the scaleni, levator 

 anguli scapulae, and rhomboid muscles. 



The posterior thoracic, called also the external respiratory 

 nerve of Mr. Bell, arises from the fourth, fifth and sixth 

 cervical nerves, passes downward and outward, behind the 

 brachial plexus and vessels, upon the scalenus posticus, 

 and ultimately terminates in the great serratus muscle. 

 This is a very long nerve, and from its origin so near 

 the phrenic, its function, according to Bell, is to associate 

 the serratus magnus muscle with the diaphragm in res- 

 piration. 



Sympathetic nerve of the neck. The sympathetic nerve is 

 so called from its extensive relation with all the various 

 parts of the body, connecting the several organs and vis- 

 cera, and uniting the whole in one harmonious action or 

 series of actions. It is also styled ganglionic, from the 

 number of ganglia which occur upon it. By Bichat it 

 was named the nervous system of organic life in con- 

 tradistinction to the cerebro-spinal or nervous system of 

 animal life. Other terms, as the intercostal, splanchnic, 



