220 CIRCULATORY SYSTEM. 



The most frequent distribution of the arteries of the hand is 

 what has just been described: anatomists are, however, not all 

 agreed on this point. It would probably be* more just to say, 

 that this occurs more frequently than any other single arrange- 

 ment. The varieties, in fact, are so great, that before a hand is 

 opened, it is not possible to know in what manner its arteries 

 will be distributed. Soretimes the Radial Artery furnishes 

 one half of the arcus sublimis, and the Ulnar the other half. 

 On other occasions, the interosseous artery is continued as a 

 large trunk over the ligament of the wrist, or the superficial 

 volae to join the arcus sublimis, and to complete the digital 

 arteries. 



SECT. IV. BRANCHES OF THE DESCENDING THORACIC AORTA. 



The Aorta, in its course from the lower part of its curvature 

 to the crura of the Diaphragm, gives off several branches to the 

 viscera and to the parietes of the thorax. 



The Bronchial Arteries (Arteries Bronchiales) are the nu- 

 tritious vessels of the lungs. There is commonly one for each 

 lung, but sometimes two or more. The right arises frequently 

 from the superior aortic intercostal artery, instead of from the 

 aorta, while the left comes from the latter: occasionally they 

 have a common root. 



On either side they follow the course of the bronchus into the 

 substance of the lung; and are distributed along with it, by ra- 

 mifications which become successively finer and finer, and 

 anastomose with the pulmonary artery; after the manner men- 

 tioned in the description of the lungs. Before they enter the 

 latter, they send some small ramifications to the posterior me- 

 diastinum, to the pericardium, and to the black bronchial glands. 



The (Esophageal Arteries (Arlerice (Esophagece) are general- 

 ly five or six small twigs which come successively from the 

 descending thoracic aorta. They ramify minutely in the sub- 

 stance of the oesophagus, communicating freely with each other: 

 the lowest of them also anastomoses around the cardia with the 

 superior coronary artery of the stomach. 



