THE THORAX. 353 



similar one from the left coronary artery. The other, the 

 interventricular, descends in the posterior (right) interven- 

 tricular groove to the apex of the heart to enter into an 

 anastomosis with the left artery. The right artery also 

 gives off several other branches to the front and side of the 

 heart (right auricle). 



The Left Coronary Artery. Figs. 70, 71, 72. 



Is given off from the left (posterior) sinus of Valsalva, 

 issues between the left auricle and the pulmonary artery, 

 curves downward in the left interventricular groove to the 

 apex of the heart to form a free anastomosis with the right 

 artery. It gives off a branch which turns backward in the 

 auriculoventricular groove to anastomose with the similar 

 branch of the right. Both arteries supply the auricles and 

 beginning of the great vessels. 



The Cardiac Veins. Figs. 70, 71, 72, 73. 



They take up the blood from the area of the heart sup- 

 plied by the above arteries, which they accompany. 



The coronary sinus extends from the anterior interventri- 

 cular vein (of which it is a continuation) around the left 

 margin of the heart to the right auricle. Near the auricle 

 it receives the right (posterior) interventricular vein. 



The anterior interventricular (great cardiac) vein follows 

 upward in the sulcus with the left artery, it reaches the 

 auriculoventricular groove, turns backward in it to the right 

 auricle, into which it empties. The portion of the vein in 

 the auriculoventricular groove is called the coronary sinus ; 

 it is about an inch long, and receives the oblique vein of 

 Marshall, posterior cardiac veins, and the posterior inter- 

 ventricular vein (accompanies the right coronary artery), 

 the last just before it enters the auricle. 

 23 



