THE HEART. 457 



upwards on the front of the right ventricle to open separately into 

 the lower part of the right auricle. 



Smallest cardiac veins. Other small veins lie in the substance of Smallest 

 the heart, and are noticed in the description of the right auricle. 



CARDIAC NERVES. The nerves for the supply of the heart are Nerves of 

 derived from a large plexus (cardiac) beneath the arch of the aorta, 

 from which offsets proceed to accompany the coronary arteries. 

 The greater part of this plexus is deeply placed, and will be 

 dissected at a later stage, but a superficial prolongation may now 

 be seen. 



The superficial cardiac plexus is placed below the arch of the aorta, Superficial 

 to the right of the ductus arteriosus (fig. 164). The nerves joining ple3 

 it are the left superficial cardiac of the sympathetic, the lower 

 cervical cardiac of the left vagus, and a considerable bundle from 

 the deep cardiac plexus. A small ganglion is sometimes seen in 

 the plexus. Inferiorly it sends off nerves along the right coronary ends in 

 artery to the heart. A few filaments also run on the left division nary. 

 of the pulmonary artery to the left lung. 



The right coronary nerves pass from the siiperficial plexus to the Coronary 

 right coronary artery, and receive near the heart a communicating 

 offset from the deep cardiac plexus. 



The left coronary nerves are derived, as will be subsequently seen, and left; 

 from the deep cardiac plexus, and follow the left coronary artery. 



At first the nerves surround the arteries, but they soon leave the ending in 

 vessels, and becoming smaller by subdivision, are lost in the muscular 

 substance of the ventricles. On and in the substance of the heart 

 the nerves are marked by small ganglia. 



The CAVITIES OF THE HEART may be examined in the order in Four cavi- 

 which the current of the blood passes through them, viz., right hSrt^ 6 

 auricle and ventricle, and left auricle and ventricle. 



Dissection. In the examination of its cavities the heart is not to Dissection 

 be removed from the body. To open the right auricle, an incision aSSSe. 

 should be made in it near the right or free border, extending from 

 the superior cava nearly to the inferior cava ; and from the centre 

 of this cut the knife is to be carried across the anterior wall to the 

 appendix. By this means an opening will be made of sufficient 

 size ; and on removing the coagulated blood, and raising the flaps 

 with hooks or pieces of string, the cavity may be examined. 



The CAVITY OF THE RIGHT AURICLE (fig. 168) is of an irregular Form of 

 form,* though when seen from the right side, with the flaps held 

 up, it has somewhat the appearance of a cone, with the base to the 

 right and the apex to the left. 



The widened part or base of the cavity is turned towards the right its base 

 side, and at its extremities are the openings of the superior and 

 inferior cavse. Between those vessels the wall projects a little, and 

 in some bodies presents a slight elevation (tubercle of Lower). The 



* The term cavity of the auricle is sometimes confined to the part in the 

 appendix, and the name atrium or sinus venosus is then given to the rest of 

 the space here named auricle. 



