Henry Gray (18251861). Anatomy of the Human Body. 1918.
Peculiarities.The ascending branch of the transverse cervical frequently arises directly from the thyrocervical trunk; and the descending branch from the third, more rarely from the second, part of the subclavian.
3. The internal mammary artery (a. mammaria interna) (Fig. 522)arises from the under surface of the first portion of the subclavian, opposite the thyrocervical trunk. It descends behind the cartilages of the upper six ribs at a distance