CARDIAC NERVES. CARDIAC PLEXUS. 535 



The Nerves of the Heart, 



Being derived from branches which have already been men- 

 tioned, are now to be described. 



They arise principally from an arrangement of nerves deno- 

 minated the Cardiac Plexus, or Plexuses, which is situated above 

 the curve of the aorta, and extends, on the posterior side of it, 

 from the root of the arteria innominata to the bifurcation of the 

 pulmonary artery. This plexus is composed of nerves which 

 are principally formed by the union of small ramifications that 

 are derived from the three above mentioned ganglions of the 

 Sympathetic Nerve, and the nerve itself; and also from the Par 

 Vagum, and some of its branches. 



These nerves are denominated the Cardiac. They descend 

 on their respective sides of the neck, but are somewhat different 

 on the different sides. On the right side three nerves have been 

 described as particularly entitled to this name, and on the left 

 side but two. 



The first on the right side is denominated Superior, or Su- 

 perficial Cardiac Nerve. It generally arises by several fine 

 threads, which unite into one delicate cord that passes down 

 by the side of the common carotid. When it has arrived on a 

 line with the middle ganglion, it sends a twig to the thyroid 

 plexus, and another that communicates with a twig from the 

 par vagum, which continues downwards on the carotid artery. 

 After passing beyond the ganglion, it divides into several 

 branches, which unite themselves to branches of the recurrent 

 nerve that are going to the middle ganglion. 



The second, which is denominated the Middle Cardiac, the 

 Great Cardiac, or the Deep Cardiac, is the largest of the three. 

 It arises from the Middle Cervical, or Thyroid Ganglion, by 

 five or six fine fibrils, which finally form one, that passes 

 before and across the subclavian ; and at that place, as well as 

 lower down, it receives twigs from the par vagum: below this, 

 it is joined by a considerable twig from the recurrent, and ter- 

 minates in the Cardiac Plexus, to which it contributes largely. 



The third cardiac nerve of the right side is called the Infe- 



