SUBCLAVIAN VEIN. 79 



hinder scaletii muscles and the fleshy slips continued upwards from the 

 erector spinae, to end beneath the complexus muscle at the posterior part of 

 the neck. 



A spinal branch (Quain) is frequently given from the second part of the 

 artery ; its offsets are continued into the spinal canal through the inter- 

 vertebral forami na. 



The SUBCLAVIAN VEIN has not the same limits as the companion artery, 

 reaching only from the lower edge of the first rib to the inner border of the 

 anterior scalenus. It is a continuation of the axillary vein, and ends by 

 joining the internal jugular in the innominate trunk. Its course is arched 

 below the level of the artery, from which it is separated by the scalenus. 



The anterior and external jugular join the subclavian vein outside the 

 scalenus, and the vertebral vein enters it inside that muscle. Into the 

 angle of union of the subclavian and jugular veins the right lymphatic duct 

 opens (fig. 27, 9 ) ; and at the like spot, on the left side, the large lymphatic 

 or thoracic duct ends (fig. 27, 8 ). The highest pair of valves in the sub- 

 clavian trunk is placed outside the opening of the external jugular vein. 1 



It should be borne in mind that not unfrequently the vein is as high in 

 the neck as the third part of its companion artery ; and that the vein has 

 been seen twice with the artery beneath the anterior scalenus. 



The ANTERIOR PRIMARY BRANCHES OF THE CERVICAL NERVES Spring 



from the common trunks in the intervertebral foramina, and appear on the 

 side of the neck between the intertransverse muscles. These nerves are 

 eight in number, and are equally divided between the cervical and the 

 brachial plexus; the highest four being combined in the former, and the 

 remaining nerves in the latter plexus. The nerves receive offsets of com- 

 munication from the sympathetic at their beginning, and intermix by means 

 of numerous branches near the spine. 



To this general statement some addition is needed for the first two nerves ; 

 and their peculiarities will be noticed in SECTION 18. 



BRACHIAL PLEXUS. The four lower cervical nerves and part of the first 

 intercostal are blended in this plexus; and a fasciculus is added to them 

 from the lowest nerve entering the cervical plexus. Thus formed, the plexus 

 reaches from the neck to the axilla, where it ends in nerves for the upper 

 limb. Only the part of it above the clavicle can now be seen. In the 

 neck the nerves have but little of a plexiform disposition: they lie at first 

 between the scaleni muscles, opposite the four lower cervical vertebras, and 

 have the following arrangement : 



The fifth and sixth nerves unite near the vertebrae ; the seventh remains 

 distinct as far as the outer border of the middle scalenus ; and the last cer- 

 vical and the piece of the first intercostal are blended in one trunk beneath 

 the anterior scalenus ; so that they make at first three cords. Near the 

 attachment of the middle scalenus to the rib, the seventh nerve throws 

 itself into the trunk of the united fifth and sixth, and then there result two 

 cords to the plexus: the one (upper) formed by the fifth, sixth, and sev- 

 enth cervical nerves ; and the other (lower) by the eighth cervical and the 

 first intercostal nerve. These two trunks accompany the subclavian artery, 

 lying to its acromial side, and are continued to the axilla where they are 

 more intimately blended. 



Branches, The branches of the plexus may be classed into those above 



1 See a paper on the Valves in the Veins of the Neck in the Edin. Med. Journal, 

 of Nov., 1856, by Dr. Struthers. 



