^ 



THE ARTERIES. 283 



3. A. subclavia sinistra (Fig. 115,/'; Fig. 1 18, <r). — The 

 left subclav^ian passes craniad from the convexity of the aortic 

 arch. It curves about the first rib (Fig. 118, /) to enter tlie 

 armpit, where it becomes the axillary artery (/). 



4. Aa. intercostales (;/). — The intercostal arteries are given 

 off from tl^e dorsal side of the aorta. Each passes to an inter- 

 costal 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, <^). 



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. cesophageae (Fig. 118, o). — The oesophageal arteries 

 are small branches of varying origin passing to the oesophagus. 



7. Aa. lumbales. — The lumbar arteries correspond to the 

 intercostals, but pass off between the lumbar vertebrae. 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, /and in\ Fig. 119, a). 



The two common carotid arteries arise from the innom- 

 inate artery in the manner already described. Each 

 passes craniad along the side of the trachea. In the thorax 

 (Fig. 118, /) the common carotid lies mediad of the sub- 

 clavian artery (Fig. 118, c) and dorsad of the superior vena 

 cava (Fig. 118, q). In the neck (Fig. 119) the artery lies, 

 accompanied by the vagus and sympathetic nerves and the 

 internal jugular vein {Jj), in the space between the longus 

 capitis muscle (7) and the trachea (u) ; it is covered ventrally 

 by the sternomastoid and sternothyroid (2) muscles, lying close 

 to the lateral border of the latter. Near its origin the common 

 carotid may give rise to the small inferior thyroid artery. It 



