976 



thj^ nervous system 



larger part of the great auricular and cervical cutaneous nerves, a branch to the 

 phrenic, a branch to the supra-clavicular nerves, and muscular branches to the 

 scalenus medius, levator scapulae, longus capitis, and trapezius (fig. 752). The 

 trapezius branch joins the spinal accessory nerve beneath the muscle. The 

 fourth nerve gives a branch to the phrenic, a branch to the supra-clavicular nerves, 

 and muscular branches to the scalenus medius, levator scapulae, longus colli, and 

 trapezius (fig. 752). The branch to the trapezius unites with the one from the 

 third nerve and joins the spinal accessory nerve beneath the muscle. 



The fibres forming the cervical (hypoglossal) loop innervate all the muscles 

 of the infra-hyoid group, though twigs to the genio-hyoid and thyreohyoid 

 seemingly enter these muscles from the trunk of the hypoglossus (fig. 752). 



Fig. 752. — Diagram of the Cervical Plexus. 



Longus capitis 

 Rectus capitis anterior 

 Rectus capitis lateralis 



Hypoglossal nerve 



Ganglion of trunk 

 of vagus 



Sterno-mastoid 

 Small occipital 



Great auricular 



Scalenus medius 



Spinal accessory 



Cervical cutaneous 



Scalenus 

 medius 



Levator scapulae 

 Sympathetic 



Superior cervical 

 sympathetic ganglion 



Genio-hyoid 



Thyreo-hyoid 



Longus colli 

 Longus capitis 

 Descendens 



cervicalis 



(hypoglossi) 

 Omo-hyoid j 



Longus colli 

 Sterno-hyoid 

 Longus capitis 



Scalenus anterior 

 S t e r n o -thyreoid 



Omo-hyoid 



Trapezius 



Posterior 

 supraclavicular 



Middle Anterior supraclavicular 



supraclavicular 



The nerve to genio-hyoid is given off from the trunk under cover of the mylo-hyoid in com- 

 mon with the terminal branches of the hypoglossal proper going to the intrinsic muscles of the 

 tongue. The nerve to the thyreo-hyoid muscles leaves the trunk of the hypoglossal near the 

 tip of the great cornu of the hyoid bone, running obliquely downward and medianward to reach 

 its muscle. A twig to the anterior belly of the omo-hyoid is given from the upper part of the 

 descendens cervicalis and the nerves for the sterno-hyoid, the sterno-thyreoid and the pos- 

 terior belly of the omo-hyoid are supplied from the turn of the loop (fig. 752). The nerves to 

 the sterno-hyoid and sterno-thyreoid send twigs downward in the muscles behiiul the manubrium 

 sterni and fibres from these in rare oases join the phrenic nerve in the thorax. The nerve to 

 the posterior Ixilly of the omo-hyoid courses as a loop in the cervical fascia below the central 

 tenclon of its nmscle. 



Each root of the cervical plexus receives a communicating grey ramus from 

 the superior cervical ganglion of the sympathetic, and from the roots and loops of 



