116 ANATOMY OF UPPER EXTREMITY, ETC. 



not always apparent if the heart has become flaccid and 

 shapeless. 



Before opening the heart the vessels 011 its surface are 

 to be dissected. They are the two coronary arteries and 

 the coronary vein. 



The CORONARY ARTERIES, two in number, are the first 

 branches of the aorta ; they emerge on the sides of the 

 pulmonary artery, and are named right and left. The right 

 coronary appears on the right side of the pulmonary artery 

 and winds round between the right auricle and ventricle to 

 the posterior aspect of the heart, where it anastomoses 

 with the left coronary artery, which has followed a similar 

 course on the left side. A branch from the right coronary 

 descends posteriorly in the sulcus between the ventricles. 

 The left coronary passes behind the pulmonary artery to 

 emerge on the left side of that vessel and winds round 

 between* the left ventricle and auricle to the back of the 

 heart, where it anastomoses with the right coronary artery. 

 The left coronary sends a branch downward to the apex of 

 the heart in the anterior sulcus between the ventricles. 



The anterior said posterior cardiac veins accompany these 

 arteries and terminate in the GREAT CARDIAC, or CORONARY 

 VEIN ; this occupies the sulcus between the right auricle 

 and ventricle posteriorly, and winding round to the front 

 terminates in a dilated ending, called the CORONARY SINUS ; 

 its termination in the sinus is marked by two valves, and 

 the sinus consists of the portion intervening between 

 these two valves and the coronary valve where it opens 

 into the right auricle. 



The nerves of the heart are furnished by the superficial 

 cardiac plexus, which surrounds the origins of the aorta and 

 pulmonary artery. The deep cardiac plexus lies between 

 the trachea and the arch of the aorta. These plexuses are 

 derived from the sympathetic and pneumogastric nerves, 

 and in them terminate the cervical cardiac branches (p. 53). 



The right auricle is opened by introducing the point of the scissors 

 into the superior vena cava, and cutting toward, and nearly to, the in- 

 ferior vena cava ; from the middle of this incision another is made 

 to the tip of the appendix. 



In the RIGHT AURICLE the following parts are to be 

 noticed : 



The endocardium is the smooth transparent lining mem- 

 brane, common to all the cavities of the heart, and con- 



