496 



ARTERIES. 



two branches ; of these, the larger runs in the groove, on the lower border of 

 the rib above ; the smaller branch along the upper border of the rib below ; 

 passing forward, they supply the Intercostal muscles, and anastomose with the 

 anterior intercostal branches of the internal mammary, and with the thoracic 

 branches of the axillary artery. The first aortic intercostal anastomoses with 

 the superior intercostal, and the last three pass between the abdominal muscles, 

 inosculating with the epigastric in front, and with the phrenic, and lumbar arte- 

 ries. Each intercostal artery is accompanied by a vein and nerve, the former 

 being above, and the latter below, except in the upper intercostal spaces, where 

 the nerve is at first above the artery. The arteries are protected from pressure 

 during the action of the Intercostal muscles, by fibrous arches thrown across, 

 and attached by each extremity to the bone. 



289. The Abdominal Aorta and its Branches. 



The posterior, or dorsal branch, of each intercostal artery, passes backwards to 

 the inner side of the anterior costo-transverse ligament, and divides into a spinal 



