BASE OP THE NECK. 59 



cialis cervicis, distributed to the under surface of the trapezius mus- 

 cle, and the posterior scapular, which passes beneath the levator anguli 

 scapulae muscle and turns downward along the base of the scapula, 

 as is described in Part Second, Dissection V. The posterior scapular 

 sometimes arises as a separate trunk from the subclavian, outside of 

 the scalenus anticus muscle ; in this case the transversalis cervicis 

 is of small size. 



The superior intercostal artery is a descending branch of the subcla- 

 vian, and can only be seen satisfactorily by cutting away the ribs in 

 front ; it turns over the neck of the first rib and supplies two, and 

 occasionally three of the upper intercostal spaces. 



The prof undo, cervicis artery usually arises in common with the pre- 

 ceding branch, although it may arise independently from the subcla- 

 viau ; it passes between the transverse processes of the seventh 

 cervical and first dorsal vertebra?, and ascends the neck between the 

 complexus and semi-spinalis colli muscles, to anastomose with a de- 

 scending branch of the occipital artery, called the princeps cervicis. 

 (See Part Second, Dissection V.) 



The internal mammary artery is a large descending branch given off 

 from the subclavian, and although sometimes arising from the thy- 

 roid axis, or in common with the subscapular, is very constant in its 

 mode of origin ; it is distributed to the inner surface of the anterior 

 portion of the thorax, and is described in Part Second, Dissection III. 



The inferior cervical ganglion, the third of the cervical 

 ganglia of the sympathetic nerve (p. 54), lies behind the 

 superior intercostal artery in the interval between the first 

 rib and the transverse process of the seventh cervical ver- 

 tebra. It is the largest of the three and irregularly rounded 

 in shape ; it is united with the middle cervical ganglion and 

 with the chain of ganglia in the thorax. It gives off the 

 inferior cardiac nerve, which, after joining the recurrent 

 laryngeal branch of the pneumogastric nerve, is continued 

 to the deep cardiac plexus lying upon the trachea, below 

 the arch of the aorta. 



The BRACHIAL PLEXUS can be better examined as to its 

 origin and plan of formation at this period of the dissec- 

 tion than in connection with the axilla. It is formed by 

 the union of the anterior branches of the last four cervical 

 and first dorsal nerves ; the fifth and sixth nerves emerging 

 from the inter- vertebral foramina descend obliquely to unite 

 in a trunk which speedily bifurcates ; the eighth cervical 

 and first dorsal ascend obliquely to unite in a large trunk 

 which also bifurcates ; the seventh continues by itself as 

 far as the first rib, and then bifurcates, one branch uniting 

 with the lower bifurcation resulting from the union of the 

 fifth and sixth nerves, and its other branch uniting with 

 the upper bifurcation resulting from the union of the eighth 



