CERVICAL NERVES. 509 



the occipital is minor runs up along the posterior border of the 

 sterno-cleido-mastoid to be distributed to the integuments of the 

 side and back part of the head. See fig. 209. 



The Third Cervical Nerve, 



Sends down, from its Anterior Branch, the principal trunk 

 of the phrenic nerve. It also sends twigs to the fourth cervi- 

 cal, to the lower cervical ganglion of the intercostal, and to the 

 descendens noni of the hypoglossal. Some of its branches 

 unite with twigs of the accessory nerve, and others are spent 

 upon the muscles and integuments of the shoulder and lower 

 part of the neck. A small Posterior Branch is spent upon the 

 muscles of the back of the neck. 



Cervical Plexus. 



The successive anastomosing loops 'and communications, 

 which take place between the branches above described as 

 coming off from the sub-occipital and the three upper cervical 

 nerves, and the neighboring nervous trunks, form a mesh or 

 network of nervous filaments that has received the name of 

 cervical plexus. This plexus is divided into the Anterior and 

 Posterior. The anterior, which is much the larger, is formed 

 from the anterior branches of the nerves. This plexus rests 

 beneath the platysma and sterno-cleido-mastoid muscles, and 

 covers the outer surface of the levator scapulae, middle sca- 

 lenus, and splenius muscles. The neighboring nerves with which 

 it has communication are the spinal accessory, the pneumogastric, 

 the sympathetic, and the hypoglossal ; it forms a junction also 

 with the descending branch of this latter nerve (descendens noni) 

 by a distinct cord called the communicans noni, which two trunks 

 form a loop over the carotid vessels. 



The posterior branches given off by each one of these same 

 cervical nerves and the sub-occipital just as they emerge from 

 the spinal column, form in a similar manner the posterior cer- 

 vical plexus, which is placed between the complexus and 

 semispinalis colli muscles. The branches forming this plexus 

 are intended as has been already described, for the sup- 

 43* 



