CIRCULATORY SYSTEM. 197 



pairs from the sides of the vessel, and are destined for the su])ply 

 of those intercostal spaces posteriorly to the last which received a 

 branch from the anterior intercostal artery. These arteries pre- 

 serve the lines of the ribs, running close to their posterior borders, 

 and expend themselves about the inferior parts of the thorax and 

 abdomen in anastomosis with the internal pectoral and epigastric 

 arteries. They furnish, near their origin, small branches which 

 enter the vertebral canal through the spinal holes ; and also 

 numerous muscular twigs during their course. 



Having detached these several small vessels, the posterior aorta 

 continues its passage between the crura of the diaphragm into the 

 cavity of the abdomen: in making its exit from the thorax, however, 

 it gives rise to two other small arteries (or else to a single branch 

 which afterwards forms two) named the 



Phrenic or diaphragmatic arteries, right and left. 

 These vessels penetrate their respective crura, in whose substance 

 they ramify, and ultimately expend themselves upon the chordi- 

 form tendon. Within the abdomen, the aorta continues to be 

 firmly attached to the spine through the medium of its several 

 vessels and cellular covering, and thus proceeds, still inclined to 

 the left side, as far as the last lumbar vertebra, underneath the 

 body of which it splits into four large arterial trunks. Prior to 

 this division, the abdominal aorta gives off" — 



I. The co^liac artery ; which is nothing more than an 

 indemonstrable stump, or rather common root, from which spring 

 the splenic, gastric, and hepatic — arteries that in some instances 

 have separate roots — whose origin is from the under part of the 

 trunk, a little posteriorly to the issue of the phrenic. 



a. The splenic artery, the middlemost of the divisions of the 

 cceliac, takes a winding course to the left side of the cavity, turns 

 forward along the greater curvature of the stomach, nmning 

 between that and the concave part of the spleen, and at length 

 ends in the left gastric artery. Soon after its origin, it gives two 

 or three twigs to the pancreas as it passes that gland ; many 

 considerable branches to the spleen from the convexity of its 

 flexure; whilst from the concavity of it are passing smaller but 

 longer branches upon the greater curvature of the stomach. It is 

 prolonged beyond the tapering termination of the spleen, dis- 

 tributing shorter branches to the stomach as it proceeds, and con- 

 tinuing to encircle the organ towards its right extremity, from 

 which is coming to inosculate with it the right gastric artery. 



b. The gastric artery, the smallest of the cceliac divisions, runs 

 forward to the small curvature of the stomach, between the layers 

 of the omentum, splitting before it reaches the organ into two 

 branches that take the names of superior and inferior gastric : 



