Fig.2. Brachial plexus, left side: root Th1 (1), root C8 is splitted into two branches (2,3), root C7 (4), root C6 (5), root C5 (6). A branch of the root C8 (2) joins the root Th1 (1); another branch of the root C8 (3) joins the root Th1 over the arteria subclavia.