m ANTHROPOLOGY. 



organs. These arteries sometimes rise from the intercostal, and are very 

 irregular in number and size. 



The oesophageal arteries are also irregular, generally three or four in 

 number. They arise from different parts of the aorta, and send branches 

 to the mediastinum and oesophagus. On the latter, some ascend, some 

 descend. The former inosculate with the cervical arteries, the latter with 

 the abdominal. 



The intercostal arteries are usually ten on the left, and nine on the right. 

 They arise from the back part of the aorta, pass obliquely outwards behind 

 the pleura, and enter the intercostal spaces ; run along the lower edge of 

 each rib between the layers of muscles, and, about the middle of the chest, 

 divide into an inferior and a superior branch. They both supply the inter- 

 costal muscles, and inosculate with the internal mammary and with the 

 thoracic arteries. Each intercostal artery, before entering the intercostal 

 space, sends a large dorsal branch backwards to the muscles on the posterior 

 part of the trunk. 



PL 135, fig. 9, arch of the aorta, with the thoracic artery : ', trachea ; 

 '■' ", branch ; \ oesophagus ; **, arch of the aorta ; ', innominata ; ', left com- 

 mon carotid ; ', left subclavian ; *, first intercostal ; '", thoracic aorta ; 

 "■", oesophageal arteries; " ", posterior bronchial; '*, an intercostal; '", its 

 anterior or intercostal branch ; ", its dorsal branch , '', a branch to the 

 medulla spinalis. Fig. 10, arteries of the spinal marrow, the anterior wall 

 of the vertebral canal removed: ', spinal marrow inclosed in its sheath; 

 ^ an intercostal artery ; ', a spinal artery entering the intervetebral foramen 

 and ramifying over the spinal marrow and its sheaths. 



E. Abdominal Aorta. 



The abdominal aorta commences below the tendinous arch, between the 

 crura of tlie diaphragm in the median line, descends with a slight obliquity 

 to the left, and divides at the lower margin of the fourth lumbar vertebra 

 into the two iliac arteries. The middle sacral may also be considered as one 

 of its terminal branches. It sends off the following branches : the phrenic, 

 coeliac axis, superior mesenteric, inferior mesenteric, renal, supra-renal, sper- 

 matic, lumbar, and middle sacral. 



1. The Phrenic Arteries arise in common or near each other, from the 

 fore part of the aorta. They both send branches to the supra-renal capsules 

 and to the crura of the diaphragm. The riglit ascends behind the vena cava, 

 the left behind the oesophagus. On the diaphragm each divides into an 

 external and an internal branch. The former passes towards the circum- 

 ference of the muscle, and inosculates with the internal mammary and the 

 inferior intercostals ; the latter enctrcles the central tendon. 



2. The Cceliac Axis arises from the fore part of the aorta opposite to 

 the last dorsal vertebra ; it soon divides into three branches. 



a. The gastric artery. This sends branches to the cardiac orifice, to the 

 oesophagus, and to the anterior and posterior surfaces of the stomach. 



h. The hepatic artery. This divides ultimately into the right and left 

 hepatic arteries. Previous to this division it gives off the superior pyloric 

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