806 THE NERVOUS SYSTEM. 



part, which lies between the trachea and aorta. The two plexuses are, however, 

 closely connected. 



The great or deep cardiac plexus (plexus magnus profundus, Scarpa) is situated 

 in front of the trachea at its bifurcation, above the point of division of the pul- 

 monary artery and behind the arch of the aorta. It is formed by the cardiac nerves 

 derived from the cervical ganglia of the sympathetic and the cardiac branches of 

 the recurrent laryngeal and pneumogastric. The only cardiac nerves which do not 

 enter into the formation of this plexus are the left superior cardiac nerve and the 

 inferior cervical cardiac branch from the left pneumogastric. 



The branches from the right side of this plexus pass, some in front of, and 

 others behind, the right pulmonary artery ; the former, the more numerous, 

 transmit a few filaments to the anterior pulmonary plexus, and are then continued 

 onward to form part of the anterior coronary plexus ; those behind the pulmonary 

 artery distribute a few filaments to the right auricle, and are then continued 

 onward to form part of the posterior coronary plexus. 



The branches from the left side of the deep cardiac plexus distribute a few 

 filaments to the superficial cardiac plexus, to the left auricle of the heart, and to 

 the anterior pulmonary plexus, and then pass on to form the greater part of the 

 posterior coronary plexus. 



The superficial (anterior) cardiac plexus lies beneath the arch of the aorta, in 

 front of the right pulmonary artery. It is formed by the left superior cardiac 

 nerve, the left (and occasionally the right) inferior cervical cardiac branches of the 

 pneumogastric, and filaments from the deep cardiac plexus. A small ganglion 

 (cardiac ganglion of Wrisberg) is occasionally found connected with these nerves 

 at their point of junction. This ganglion, when present, is situated immediately 

 beneath the arch of the aorta, on the right side of the ductus arteriosus. The 

 superficial cardiac plexus forms the chief part of the anterior coronary plexus, arid 

 several filaments pass along the pulmonary artery to the left anterior pulmonary 

 plexus. 



The posterior or right coronary plexus is chiefly formed by filaments prolonged 

 from the left side of the deep cardiac plexus, and by a few from the right side. It 

 surrounds the branches of the coronary artery at the back of the heart, and its 

 filaments are distributed with those vessels to the muscular substance of the 

 ventricles. 



The anterior or left coronary plexus is formed chiefly from the superficial cardiac 

 plexus, but receives filaments from the deep cardiac plexus. Passing forward 

 between the aorta and pulmonary artery, it accompanies the left coronary artery 

 on the anterior surface of the heart. 



Valentin has described nervous filaments ramifying under the endocardium ; 

 and Remak has found, in several mammalia, numerous small ganglia on the cardiac 

 nerves, both on the surface of the heart and in its muscular substance. 



The Epigastric or Solar Plexus (Figs. 425, 427). 



The Epigastric or Solar plexus supplies all the viscera in the abdominal cavity. 

 It consists of a great network of nerves and ganglia, situated behind the stomach 

 and in front of the aorta and crura of the Diaphragm. It surrounds the coeliac 

 axis and root of the superior mesenteric artery, extending downward as low as the 

 pancreas and outward to the suprarenal capsules. This plexus, and the ganglia 

 connected with it, receive the great and small splanchnic nerves of both sides, 

 and some filaments from the right pneumogastric. It distributes filaments which 

 accompany, under the name of plexuses, all the branches from the front of the 

 abdominal aorta. 



Of the ganglia of which the solar plexus is partly composed the principal are 

 the two semilunar ganglia, which are situated one on each side of the plexus, and 

 are the largest ganglia in the body. They are large irregular gangliform masses 

 formed by the aggregation of smaller ganglia, having interspaces between them. 



