The =axillary nerve= (Figs. 441, 520), also termed the circumflex,
derives its fibers from the eighth cervical and first thoracic roots of
the brachial plexus. It runs downward and backward across the lower part
of the subscapularis and dips in between that muscle and the subscapular
artery at the level of the shoulder joint. Continuing outward in the
interval between the teres minor and the long and external heads of the
triceps, it reaches the deep face of the deltoid and divides into
several divergent branches. The =muscular branches= supply the teres
major, capsularis, teres minor, infraspinatus, deltoid, and
mastoido-humeralis. The =cutaneous branch= (N. cutaneus brachii
lateralis) runs downward and a little forward across the external head
of the triceps and ramifies on the fascia on the front of the forearm
and on the superficial pectoral muscle.