492 NERVOUS SYSTEM. 



of the phrenic nerve ; another filament from it joins the supe- 

 rior cervical ganglion of the sympathetic. 



Of the Third Cervical Nerve. 



This nerve comes out between the third and the fourth cer- 

 vical vertebra. Its posterior fasciculus is distributed to the mus- 

 cles on the back of the cervjcal vertebrae, and to the integu- 

 ments of the part; anastomosing, by its branches, with the nerve 

 above and below. 



The anterior fasciculus is larger than the posterior, and goes 

 obliquely downwards and outwards at first; it sends anastomo- 

 tic branches to the nerve above and below ; it also anastomoses 

 with the superior cervical ganglion of the sympathetic and with 

 the descendens noni. One of its branches, being joined by the 

 branch just spoken of, from the second cervical nerve, consti- 

 tutes the root of the phrenic nerve. But the principal number 

 of its branches are distributed to the integuments along the cla- 

 vicle, (nervi supra-clavicular es,) the upper part of the sternum* 

 and the shoulder; some of them going into the contiguous mus- 

 cles, as the trapezius, subclavius, &c. Several anastomoses 

 exist between the branches of this nerve and the terminating 

 branches of the nervus accessorius. 



The three preceding cervical nerves form, by their anasto- 

 moses with each other, a plexus, consisting in a number of large 

 loops or arches, which lie upon the sides of the muscles con- 

 nected with the transverse processes of the cervical vertebra. 

 There are, commonly two series of anastomoses: the branches 

 of the first series, form the second series, and from the latter 

 proceed, for the most part, the several branches which have been 

 described. These anastomoses are covered by the upper half 

 of the sterno-cleido- mastoid muscle, are involved in the cellular 

 membrane surrounding the great vessels of the neck, and are 

 covered by the lymphatic glands. Their intertexture and dis- 

 tribution are such, that no adequate idea of them can be con- 

 veyed without dissection. From this plexus several branches 

 go to the sterno-mastoid muscle, and it is united above to the 

 sub-occipital nerve and below to the fourth cervical. 



