AN ATOM Y OF THE HEART AND BLOOD - VESSELS. 219 



diaphragm it enters the abdomen and after supplying the 

 parts in and around that cavity with branches, it ends oppo- 

 site the last lumbar vertebra by dividing into the right and 

 left common iliac arteries, which carry blood to the lower 

 limbs. We have then to consider the branches of the arch of 

 the aorta, and those of the descending aorta > which latter is 

 for convenience described by anatomists as consisting of the 

 thoracic aorta, extending from the end of the arch to the., 

 diaphragm, and the abdominal aorta, extending from the 

 diaphragm to the final subdivision of the vessel. 



Branches of the Arch of the Aorta. From this arise first 

 the coronary arteries (crd and crs, Figs. 90 and 91) which 

 spring close to the heart, just above two of the pouches of the 

 eemilunar valve, and carry blood into the substance of that 

 organ. The remaining branches^ of the arch are three in 

 number, and all arise from its convexity. The first is the 

 innominate artery (AT), Fig. 90), which is very short, imme- 

 diately breaking up into the right subclavian artery, and the 

 right common carotid. Then comes the left common carotid, 

 Cs, and finally flie left subclavian, Ssi. 



Each subclavian artery runs out to the arm on its own 

 side and after giving off a vertebral artery (which runs up 

 the neck to the head in the vertebral canal of the transverse 

 processes of the cervical vertebrae), crosses the arm-pit and 

 takes there the name of the axillary artery. This contin- 

 ues down the arm as the brachial artery, which, giving off 

 branches on its way, runs to the front of the arm, and just 

 below the elbow T -joint divides into the radial and vlnar ar- 

 teries, the lower ends of which are seen at R and U in Fig. 88. . 

 These supply the forearm and end in the hand by uniting to 

 form an arch, from which branches are given off to the fingers. 



The common carotid arteries pass out of the chest into the 

 neck, along which they ascend on the sides of the windpipe. 

 Opposite the angle of the lower jaw each divides into an 

 internal arid external carotid artery, right or left as the case 

 may be. The external ends mainly in branches for the face, 

 scalp, and salivary glands, one great subdivision of it with a 

 tortuous course, the temporal artery, being often seen in thin 

 persons beating on the side of the brow. The internal carotid 

 artery enters the skull through an aperture in its base and 

 supplies the brain, which it will be remembered also gets 

 blood through the vertebral arteries. 



