THE ANTERIOR PART OF THE NECK 141 



should trace the remains of the lesser occipital, the great auricu- 

 lar, the nervus cutaneus colli and the supraclavicular branches, 

 which he displayed in the posterior triangle, to their origins 

 from the roots of the plexus. The communicating branches 

 which pass forwards to the descendens hypoglossi from the 

 second, and sometimes also from the third cervical nerve, must 

 be followed ; they may cross either superficial or deep to the 

 internal jugular vein. Then the phrenic nerve, which springs 



Lesser occipital i R 



Great auricular, 



Nervus cutaneus colli 



Branch to levator 

 scapulae 



Branch to levator 

 scapulae 



Descending trunk 



Hypoglossal 



To genio-hyoid 



c c u Thyreo-hyoid nerve 



Descendens hypoglossi 



Ansa hypoglossi 



eating to 

 fifth cervical 



Phrenic 



FIG. 50 Diagram of the Cervical Plexus and the Ansa Hypoglossi. 

 I, II, III, IV. Anterior rami of the upper four cervical nerves. 



R. Branches to recti and longus capitis. 

 S. M. Branches to the sterno-mastoid. 

 C.C. Rami communicantes cervicales. 



C.H. Communicating branch to hypo- 

 glossal. 



This diagram shows that the descendens hypoglossi, the branch to the 

 thyreo-hyoid, and in all probability the branches to the genio-hyoid, are 

 composed of fibres given to the hypoglossal by the communicating twigs 

 it receives from the first cervical nerve. 



from the fourth cervical nerve, and receives additional twigs 

 from the third and fifth nerves, must be followed downwards 

 and medially, till it disappears under cover of the lower part of 

 the internal jugular vein. It lies upon the surface of the scalenus 

 anterior and passes deep to the omo-hyoid muscle and the 

 transverse cervical and transverse scapular arteries. Running 

 upwards parallel with, and anterior to it, is the ascending cervical 

 branch of the inferior thyreoid artery. 



Plexus Cervicalis. The cervical plexus is a looped plexus 

 formed by the first four cervical nerves. It lies in the upper 



