258 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



chest wall and continues on the abdomen as the superior epigastric artery. At 

 the same level from the posterior surface of the subclavian, practically in common 

 with the preceding, the supreme intercostal artery arises. It runs posteriorly on 

 the dorsal wall of the thorax and receives the first intercostal arteries. On its 

 anterior surface at about the same level as these the subclavian artery gives rise 

 to the vertebral artery which passes immediately dorsad toward the cervical ver- 

 tebrae where it enters the vertebrarterial canal; and to the superficial cervical 

 artery which ascends in the lateral part of the neck, supplying various muscles, 

 its main branch (ascending cervical) accompanying the external jugular vein. 

 The transverse artery of the neck leaves the subclavian at the same place or in 

 common with the supreme intercostal artery. It passes dorsally in front of the 

 first rib through a loop formed by two nerves, and emerges on the medial side 

 of the serratus ventralis muscle. It is best found by looking on this muscle and 

 then tracing the artery toward the subclavian. After giving off the foregoing 

 branches the subclavian passes in front of the first rib into the axilla where it 

 is named the axillary artery. This lies between two of the stout nerves belong- 

 ing to the brachial plexus. Its branches are similar to those of the axillary vein 

 and accompany the veins. After giving rise to the small thoracoacromial artery 

 to the pectoral and deltoid muscles, the axillary gives off the long thoracic and 

 subscapular arteries, accompanying the veins previously described. The former 

 runs posteriorly along the serratus muscle and then as the external mammary 

 artery passes to the under surface of the skin of the lateral abdominal wall, being 

 especially conspicuous in females. (Most of this vessel was destroyed in remov- 

 ing the skin.) The subscapular has a conspicuous branch (thoracodorsal artery) 

 passing caudad to the latissimus dorsi and cutaneous maximus muscles; it 

 then turns dorsally and perforating the teres major emerges on the outer surface 

 of the shoulder, supplying various muscles. Near the point of origin of the 

 subscapular the deep artery of the arm arises, and after giving off branches into 

 the subscapular muscle passes between this muscle and the teres major to the 

 dorsal part of the arm where it runs in company with one branch of the cephalic 

 vein and a nerve, all three situated internal to the lateral head of the triceps which 

 should be deflected. The axillary artery now passes to the upper arm, where as 

 the brachial artery it courses along the inner surface of the limb in company 

 with the brachial vein and nerves. 



Draw the branches of the subclavian. 



Cat: At the level of the first rib the subclavian has four branches: internal 

 mammary, vertebral, costocervical axis, and thyrocervical axis. The internal mam- 

 mary springs from the ventral surface of the subclavian, accompanies the cor- 

 responding vein along the chest wall, and passes on to the abdominal wall as 

 the superior epigastric artery. The vertebral artery arises from the dorsal sur- 

 face of the subclavian and passes dorsally into the vertebraterial canal, giving 

 off small branches into the neck muscles. The costocervical axis divides in two 

 almost at once. One branch, the supreme intercostal artery, passes posteriorly 



