612 tee arteries. 



2. Lumbar Arteries. 



These are five-or six in number, and do not differ in their general arrange- 

 ment from the intercostal arteries ; they having the same mode of origin, the 

 same division into two branches, and the same distribution. The superior, or 

 lumho-spinal branch, is much larger than the inferior, and goes to the muscles 

 and integuments of the lumbar region ; it also furnishes a branch to the spinal 

 cord. The inferior branch passes above the large and small psoas muscles, giving 

 them numerous twigs, and extending to the muscular portions of the transverse 

 and small oblique abdominal muscles, where their ramifications anastomose with 

 those of the circumflex iliac artery. 



The last, and sometimes also the second-last, lumbar artery arises from the 

 internal iliac trunk ; the others emerge directly from the iliac aorta. 



3. Diaphragmatic (or Phrenic) Arteries. 



These are two or three small vessels which spring from the aorta as it passes 

 between the two pillars of the diaphragm, and are destined for that muscle. 

 The left pillar receives a very insignificant branch, but the right has two, the 

 most considerable of which is alone constant ; it sometimes sends subpleural 

 ramuscules to the right lung. 



4. Middle Sacral (Sacra Media) Artery. 



This vessel is often absent, and when it exists is very variable in size, though 

 always extremely slender. It arises from the terminal extremity of the aorta, 

 in the angle comprised between the two internal iliac arteries, and is carried to 

 the inferior face of the sacrum, where it is expended in lateral ramifications 

 which go to the periosteum. It has been thought necessary to notice this artery, 

 as it attains a considerable volume in Man and some animals, and continues the 

 aortic ramifications beneath the sacral portion of the vertebral column. 



Visceral Branches of the Posterior Aorta. 



1. Broncho-(ESOPHAGeal Artery (Fig. 318, m). 



Destined for the lung, the visceral pleura, the mediastinum, and the oeso- 

 phagus, this arteiy arises, not, as is generally said, in the concavity of the arch 

 of the aorta, but opposite to it, and very near, but to the right of, the first pair 

 of intercostals ; often even in common with these arteries and with the second 

 pair.^ After leaving the aorta, it insinuates itself between that trunk and the 

 oesophagus, and above the bifurcation of the trachea divides into branches, the 

 hronchial arteries. In its short course, it gives off the two esophageal arteries 

 and a certain number of innominate ramuscules. 



Bronchial Arteries. — The disposition of these two vessels is extremely 

 simple ; they enter the lung with the bronchi — one to the right, the other to 

 the left — and there break up into arborescent ramifications that follow the air- 

 tubes to the pulmonary lobules. 



(Esophageal Arteries. — These two arteries are placed in the posterior 

 mediastinum, one above, the other below the oesophagus, which they accompany 

 for a short distance backwards, to the extremity of that canal. 



' See Intercostals. 



