THE CERVICAL PLEXUS. 577 



CERVICAL PLEXUS. 



The cervical plexus is formed by the anterior divisions of the first 

 four cervical nerves, and distributes branches to some of the muscles of 

 tlie neck, and to a portion of the integument of the head and neck. It 

 is placed opposite the first four vertebrae, beneath the sterno-mastoid 

 muscle, and rests against the middle scalenus muscle and the levator 

 anguli scapulae. The disposition of the nerves in the plexus is easily 

 recognised. Each nerve, except the first, branches into an ascending 

 and a descending part : and these are united in communicating loops 

 "n-ith the contiguous nerves. From the union of the second and third 

 nerves, superficial branches are supplied to the head and neck ; and from 

 the junction of the third with the fourth, arise the cutaneous nerves of 

 the shoulder and chest. Muscular and coimnunicating branches spring 

 from the same nerves. 



The BRANCHES of the plexus may be separated into two sets — a 

 superficial and deep ; the superficial consisting of those which ramify- 

 over the cervical fascia, supplying the integument and some also the 

 platysma ; the deep comprising branches which are distributed for the 

 most part to the muscles. The superficial nerves may be subdivided 

 into ascending and descending ; the deep nerves into an internal and 

 external series. 



Superficial Ascending Branches. 



Superficial cervical nerve. — This nerve takes origin from the 

 second and third cervical nerves, turns forward over the sterno-mastoid 

 muscle about the middle, and, after perforating the cervical fascia, 

 divides beneath the platysma myoides into two branches, which are dis- 

 tributed to the anterior and lateral parts of the neck. 



a. The npper hrancTi gives an ascending' twig which accompanies the external 

 jugular vein, and communicates freely with the facial nerve (cervico-facial 

 division) ; it is then transmitted through the platysma to the surface, supplying 

 that muscle, and ramifies in the integument of the upper half of the front of 

 the neck, filaments reaching as high as the lower maxilla. 



h. The lojver branch likewise pierces the platysma, and is distributed below 

 the preceding, its filaments extending in front as low as the sternum. 



The superficial cervical nerve may arise from the plexus in the form of two or 

 more distinct branches. Thus Valentin describes thi'ee superficial cervical 

 nerves, which he names superior, middle, and inferior. ('• Sommerring v. Bau,"' 

 &c.) 



"While the superficial cervical nei-ve ramifies over the platysma myoides, the 

 facial nerve is beneath the muscle. According to Valentin many anastomotic 

 arches are fonned on the side of the neck between those two nerves, as well as 

 between the branches of the former, one with another 



Great aiiricular nerve. — This nerve winds round the outer border 

 of the sterno-mastoid, and is directed obliquely upwards beneath the 

 platysma myoides, between the muscle and the deep fascia of the neck, 

 to the lobe of the ear. Here the nerve gives a few small branches to 

 the face, and ends in the auricular and mastoid branches. 



a. The auricular branches are directed to the back of the external ear, en 

 which they ramify, and are connected with twigs derived from the facial nerve. 

 One of these branches reaches the outer surface of the ear by a fissure between 

 the antihelix and the concha. A few filaments are supplied likewise to the outer 

 part of the lobule. 



VOL. I. p p 



