_a_, aorta (_a′_, aortic arch); _b_, innominate artery; _c_, left subclavian; _d_, right subclavian; _e_, right common carotid; _f_, left common carotid; _g_, costocervical axis; _g′_, vertebral artery; _h_, internal mammary artery; _i_, axillary artery; _j_, thyrocervical axis; _k_, A. transversa scapulæ; _m_, mediastinal artery; _n_, intercostal arteries; _o_, œsophageal arteries; _p_, left coronary artery; _q_, superior vena cava; _r_, internal mammary vein; _s_, the two innominate veins; _t_, sternal artery; _u_, costocervical vein; _v_, vertebral vein; _w_, axillary vein; _x_, vein to clavotrapezius and lateral ends of the pectoral muscles; _y_, vein accompanying second branch of A. transversa scapulæ; _z_, thyrocervical vein. 1, external jugular vein; 2, internal jugular vein; 3, vena cordis magna; 4, œsophagus; 5, thoracic duct; 6, one of the lymphatic ducts from the neck. _I_, first rib (cut); _VIII_, eighth rib (cut); _XII_, twelfth rib (cut).] 3. =A. subclavia sinistra= (Fig. 115, _k_; Fig. 118, _c_).--The left subclavian passes craniad from the convexity of the aortic arch. It curves about the first rib (Fig. 118, _I_) to enter the armpit, where it becomes the =axillary artery= (_i_). 4. =Aa. intercostales= (_n_).--The intercostal arteries are given off from the dorsal side of the aorta. Each passes to an intercostal space and divides into three branches. One of these passes ventrad along the caudal margin of the cranial one of the two ribs between which it extends. Another goes to the deep muscles of the back, and the third enters the spinal canal through the intervertebral foramen. The arteries for the first and second (and sometimes the third) intercostal space usually arise from the subclavian (costocervical axis, Fig. 118, _g_). 5. =Aa. bronchiales.=--The bronchial arteries are two, and arise either from the aorta opposite the fourth intercostal space or from the fourth intercostal arteries. They accompany the bronchi to the lungs. 6. =Aa. œsophageæ= (Fig. 118, _o_).--The œsophageal arteries are small branches of varying origin passing to the œsophagus. 7. =Aa. lumbales.=--The lumbar arteries correspond to the intercostals, but pass off between the lumbar vertebræ. The obliquity of the diaphragm throws the origin of one or two pairs of them within the thorax. A. CAROTIS COMMUNIS. THE COMMON CAROTID ARTERY. (Fig. 115, _l_ and _m_; Fig. 119, _a_).