BRANCHES OF THE THORACIC AORTA. 297 



anterior and posterior aspects of the wrist-joint, where they inoscu- 

 late with corresponding branches of the radial artery. 



The Digital branches are given off from the superficial palmar 

 arch, and are four in number. The first and smallest is distributed 

 to the ulnar side of the- little finger. The other three are short 

 trunks, which divide between the heads of the metacarpal bones, 

 and form the collateral branch of the radial side of the little finger, 

 the collateral branches of the ring and middle fingers, and the col- 

 lateral branch of the ulnar side of the index finger. 



The Superficial palmar arch receives the termination of the deep 

 palmar arch from between the abductor \minimi digiti and flexor 

 brevis minimi digiti near to their origins, and terminates by inoscu- 

 lating with the superficialis votse upon the ball of the thumb. The 

 communication between the superficial and deep arch is generally 

 described as the communicating branch of the ulnar artery. 



The mode of distribution of the arteries to the hand is subject to 

 great variety. 



BRANCHES OF THE THORACIC AORTA. 



Bronchial, 



(Esophageal, 



Intercostal. 



The BRONCHIAL ARTERIES are four in number, and vary both in 

 size and origin. They are distributed to the bronchial glands and 

 tubes, and send branches to the ossophagus, pericardium, and left 

 auricle of the heart. These are the nutritious vessels of the lungs. 



The (ESOPHAGEAL ARTERIES are numerous small branches ; they 

 arise from the anterior part of the aorta, are distributed to the oeso- 

 phagus, and establish a chain of anastamosis along that tube : the 

 superior inosculate with the bronchial arteries, and with cesophageal 

 branches of the inferior thyroid arteries ; and the inferior with 

 similar branches of the phrenic and gastric arteries. 



The INTERCOSTAL, or posterior intercostal arteries, arise from the 

 posterior part of the aorta ; they are nine in number on each side, 

 the two superior spaces being supplied by the superior intercostal 

 artery, a branch of the subclavian. The right intercostals are longer 

 than the left, on account of the position of the aorta. They ascend 

 somewhat obliquely from their origin, and cross the vertebral column 

 behind the thoracic duct, vena azygos major, and sympathetic nerve, 

 to the intercostal spaces, the left passing beneath the superior inter- 

 costal vein, the vena azygos minor and sympathetic. In the inter- 

 costal spaces, or rather, upon the external intercostal muscles, each 

 artery gives off a dorsal branch, which passes back between the 

 transverse processes of the vertebrae, lying internally to the middle 

 costo-transverse ligament, and divides into a spinal branch, which 

 supplies the spinal cord and vertebras, arid a muscular branch which 

 is distributed to the muscles and integument of the back. It then 

 comes into relation with its vein and nerve, the former being above, 

 and the latter below, an$ divides into two branches which run along 



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