624 THE HEART. 



The right coronary artery arises above the anterior semi- 

 lunar valve in front of the aorta, makes its appearance 

 "between the right auricle and ventricle, and following the 

 course of the groove between these two to the posterior 

 part, distributes branches as it proceeds to the right auricle 

 and right ventricle. 



The left coronary artery comes from above the left semi- 

 lunar valve, and, while concealed by the pulmonary artery, 

 divides into two branches, a superior and inferior. The 

 superior passes round the groove between the left auricle 

 and left ventricle to the back of the heart, and supplies 

 these two cavities with branches. The inferior division 

 descends along the septum of the ventricles to the apex of 

 the heart, supplying with branches both ventricles, and 

 anastomosing freely with the other coronary branches. 



The coronary veins return the blood of the heart, and 

 are distinguished into the greater and lesser coronary. The 

 greater coronary vein begins at the apex of the heart, by the 

 union of several branches, and then ascends along the an- 

 terior septum of the ventricle, to terminate finally in the 

 right auricle, at its posterior inferior part, to the left of the 

 inferior cava, where it is guarded by a valve. Throughout 

 its whole course it is constantly receiving streams. 



The lesser coronary vein returns the blood, mostly of the 

 right ventricle, and discharges it into the greater coronary 

 just as the latter is entering the right auricle. Some 

 smaller veins are also described about the roots of the aorta 

 and pulmonary artery, discharging into the right auricle 

 by several orifices. 



The nerves of the heart come principally from the cardiac 

 plexus of the sympathetic, and follow the course of the 

 coronary arteries. Branches also are traced from the par 

 vagum. 



Function. The office of the heart has already been stated 

 to be, to circulate the blood, in which function it is the 

 prime agent. The venous blood is returned from all parts 

 of the body by the ascending and descending cava, and 

 coronary vein, into the right auricle of the heart. This 



