A long slender nerve situated on the side of the chest beneath the panniculus and above the spur vein, whose course it follows, to be lost in the panniculus of the flank. It is formed mainly of the dorsal roots of the thoracic plexus, and to a small extent from the eighth cervical nerve. In its course backwards it gives off branches which anastomose with the second and third perforating intercostal nerves, and forms a net-work over the inner surface of the panniculus. The panniculus extending over the shoulder and arm receives fibres from this nerve.