CARDIAC NERVES. 487 



canal, forming the vertebral plexus. This plexus sends filaments to all 

 the branches given off by the artery, and communicates in the cranium 

 with the filaments of the carotid plexus accompanying the branches of 

 the internal carotid artery. 



The internal branch is the inferior cardiac nerve, nervus cardiacus 

 minor. 



CARDIAC NERVES.* The superior cardiac nerve (nervus super- 

 Jicialis cordis) arises from the lower part of the superior cervical 

 ganglion ; it then descends the neck behind the common carotid artery 

 and parallel with the trachea, crosses the inferior thyroid artery, and 

 running by the side of the recurrent laryngeal nerve for a short dis- 

 tance, passes behind the arteria innominata to the concavity of the 

 arch of the aorta, where it joins the cardiac ganglion. 



In its course it receives branches from the pneumogastric nerve, and 

 sends filaments to the thyroid gland and trachea. 



The Middle cardiac nerve (nervus cardiacus magnus) proceeds 

 from the middle cardiac ganglion, or, in its absence, from the cord of 

 communication between the superior and inferior. It is the largest 

 of the three nerves, and lies nearly parallel with the recurrent larvn- 

 geal. At the root of the neck it divides into several branches, which 

 pass some before and some behind the subclavian artery ; it com- 

 municates with the superior and inferior cardiac, and with the pneu- 

 mogastric and recurrent nerves, and descends to the bifurcation of the 

 trachea, to the great cardiac plexus. 



The Inferior cardiac nerve (nervus cardiacus minor) arises from 

 the inferior cervical ganglion, communicates freely with the recurrent 

 laryngeal and middle cardiac nerves, and descends to the front of the 

 bifurcation trachea, to join the great cardiac plexus. 



The Cardiac ganglion is a ganglionic enlargement of variable size, 

 situated beneath the arch of the aorta, to the right side of the liga- 

 ment of the ductus arteriosus. It receives the superior cardiac nerves 

 of opposite sides of the neck and a branch from the pneumogastric, 

 and gives off numerous branches to the cardiac plexuses. 



The Great cardiac plexus is situated upon the bifurcation of the 

 trachea, above the right pulmonary artery, and behind the arch of the 

 aorta. It is formed by the convergence of the middle and inferior 

 cardiac nerves, and by branches from the pneumogastric and descen- 

 dens noni nerve, and first thoracic ganglion. 



The Anterior cardiac plexus is situated in front of the ascending 

 aorta, near its origin. It is formed by the communications of filaments 

 that proceed from three different sources, namely, from the superior 

 cardiac nerves, crossing the arch of the aorta ; from the cardiac ganglion 

 beneath the arch ; and from the great cardiac plexus, passing between 

 the ascending aorta and the right auricle. The anterior cardiac plexus 



* There is no constancy with regard to the origin and course of these nerves ; 

 therefore the student must not be disappointed in finding the description in 

 discord with his dissection. 



