Chap. XI] THE VASCULAR SYSTEM 193 



the ulnar and radial arteries. It may be readily located, b'ing 

 in the depression along the inner border of the biceps muscle. 

 Pressure made at this point from within outward against the 

 humerus will control the blood supply to the arm. 



The ulnar, the larger of the two vessels into which the brachial 

 divides, extends along the inner side of the forearm into the palm 

 of the hand, where it terminates in the superficial palmar arch. 



The radial artery appears, by its direction, to be a continuation 

 of the brachial, although it does not equal the ulnar in size. It 

 extends along the outer side of the front of the forearm as far as 

 the lower end of the radius, below which it turns around the outer 

 border of the wrist, and passes forward into the palm of the hand. 

 It terminates in the deep palmar arch. The superficial and deep 

 palmar arches anastomose and supply the hand with blood. 



Thoracic aorta. — The branches derived from it are numerous 

 but small. The principal ones are : — • 



(1) The intercostal arteries are ten or eleven on each side. 

 They arise from the aorta and extend outward to the intercostal 

 spaces. They give off branches to supply the muscles of the back 

 and chest, the pleurae, the spinal cord and its membranes, and also 

 the vertebral column. Branches from the third, fourth, fifth, 

 and sixth supply the mammary glands. (See page 453.) 



(2) The pericardial arteries pass to the pericardium and supply 

 it with blood. 



(3) The bronchial arteries are three in number and pass one 

 to the right and two to the left lung. Branches from these arteries 

 ramify through the lung tissue and supply it with nutritive material. 

 Branches are also distributed to the bronchial tubes, oesophagus, 

 and pericardium. 



(4) The oesophageal arteries are four or five in number and 

 supply the oesophagus. 



(5) The posterior mediastinal arteries pass backward between 

 the lungs to the thoracic vertebra and supply the lymph nodes 

 found in the mediastinum. (See page 242.) 



Abdominal aorta. — It gives off numerous branches, which may 

 be divided into two sets : — 



1. Visceral, or those which supply the viscera. 



2. Parietal, or those which are distributed to the walls of the 

 abdomen. 



