THE COMMON CAROTID ARTERY 541 



branches arc detached. Tlie intercostal branches (Rami intercostales) pass 

 upward in the intercostal spaces and anastomose with homonymous descending 

 arteries. The h)wer branches detach small twigs to the transversus thoracis, ]ileura, 

 and i^ericardium, and pass out between the costal cartihiges as perforating branches 

 (Rami i)erforantes) to supply the pectoral muscles and skin, anastomosing with 

 the external thoracic artery. A very small pericardiaco-phrenic artery ascends in 

 the media.stinum on the left side, in the caval fold of pleura on the right side; it 

 supplies fine twigs to the pericardium and pleura and accompanies the phrenic 

 nerve to the diaphragm. In the young subjcM-t it gives snuill branches (Aa. 

 thymicse) to the thymus gland. The asternal artery (A. musculophrenica) passes 

 along the ninth costal cartilage and continues along the costal attachment of the 

 transversus abdominis (Fig. 185). It gives off intercostal branches which anas- 

 tomose with those descending from the thoiacic aorta, and twigs to the diapiiragm 

 and transversus alxlominis. The anterior abdominal artery (A. epigastrica 

 cranialis) is the direct continuation of the internal thoracic. It passes be- 

 tween the ninth costal cartilage and the xiphoid cartilage, runs backward on the 

 abdominal surface of the r(H'tus abdominis and then becomes embedtled in it 

 (Fig. 466). It supplies the ventral wall of the abdomen and anastomoses with 

 the posterior abdominal artery. 



5. The external thoracic artery (A. thoracica externa) is given off from th(> 

 ventral aspect of the braciiial, usually at the inner surface or anterior l)order of 

 the first rib. It turns around the first rib below or behind the brachial vein (when 

 given off within the thorax) and pa.sses backward under the deep pectoral muscle; 

 it is continued as a small vessel in the panniculus carnosus, w^here it accompanies 

 the external thoracic ("spur") vein. It sends branches to the pectoral muscles 

 and the axillary lymph glands. 



This artery varies in origin and size. Not rarely it arises from the internal thoraeic or 

 from tlie brachial outside of the thorax. In other ca.scs it ari.ses by a common trunk with the 

 inferior cervical. It may be very small or even absent, in which case the perforating branches 

 of the internal thoracic compensate. 



6. The inferior cervical artery (Truncus omo-cervicalis) ari.ses usually from 

 the dorsal siu'face of the brachial opposite the first ril) or where that vessel winds 

 around the rib. It is directed downward and a little forward across the external 

 surface of the jugular vein and the deep face of the scalenus among the lymph 

 glands at the thoracic inlet, and divides into ascending and descending branches. 

 The ascending branch (A. cervicalis ascendens) passes upward and forward along 

 the external surface of the jugular vein, then turns sharply backward and runs 

 upward along the anterior border of the anterior deep pectoral muscle, between the 

 omo-hyoideus and mastoido-humeralis and in relation to the prescapular lymph- 

 glands; it gives branches to these muscles and the prepectoral and prescapular 

 lymph glands. The descending branch (A. transversa scapulae) passes downward 

 and outward across the surface of the anterior deep pectoral and then runs in the 

 groove between that muscle and the mastoido-humeralis in company with the 

 cephalic vein. It supplies branches to these muscles and the skin of the breast. 



THE COMMON CAROTID ARTERY 



These two vessels (ArteritB carotides communes) arise from the brachio- 

 cephalic artery by a common trunk. This stem, the truncus bicaroticus or cephalic 

 artery, is detached from the inner face of the brachiocephalic opposite the first rib 

 and passes forward in the median plane beneath the trachea. It is related ventrall}" 

 to the prepectoral Ij^mph glands, the terminal parts of the jugular veins, and the 

 anterior vena cava, and laterally to the vagus and recurrent nerves. It is commonly 



