668 SYMPATHETIC NERYE. 



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 continued 

 along the trunk of the pulmonary artery, to form part of the anterior coronary 

 plexus; those behind the pulmonary artery distribute a few filaments to the 

 right auricle, and form part of the posterior coronary plexus. 



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

 filaments to the left auricle of the heart and the anterior pulmonary plexus, 

 and then pass on to form the greater part of the posterior coronary plexus, a 

 few branches passing to the superficial cardiac 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 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 arte- 

 riosus. The superficial cardiac plexus forms the chief part of the anterior 

 coronary plexus, and several filaments pass along the pulmonary artery to the 

 left anterior pulmonary plexus. 



The posterior 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 coronary plexus is formed chiefly from the superficial cardiac 

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

 between the aorta and pulmonary artery, it accompanies the right 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 elaborate dissections lately completed by Dr. Robert Lee have demon- 

 strated without any doubt the existence of a dense mesh of nerves distributed 

 both to the surface, and in the substance of the heart, having numerous ganglia 

 developed upon them. 



THORACIC PART OF THE SYMPATHETIC. 



The Thoracic .Portion of the Sympathetic consists of a series of ganglia, 

 which usually correspond in number to that of the vertebra?; but, from the 

 occasional coalescence of two, their number is uncertain. These ganglia are 

 placed on each side of the spine, resting against the heads of the ribs, and 

 covered by the pleura costalis : the last two are, however, anterior to the rest, 

 being placed on the side of the bodies of the vertebras. The ganglia are small 

 in size, and of a grayish color. Ths first, larger than the rest, is of an elongated 

 form, and usually blended with the last cervical. They are connected together 

 by cord-like prolongations from their substance. 



The external branches from each ganglion, usually two in number, communi- 

 cate with each of the dorsal spinal nerves. 



The internal branches from the six upper ganglia are very small: they supply 

 filaments to the thoracic aorta and its branches, besides small branches to the 

 bodies of the vertebrae and their ligaments. Branches from the third and fourth 

 ganglia form part of the posterior pulmonary plexus. 



The internal branches from the six lower ganglia are large and white in color; 

 they distribute filaments to the aorta, and unite to form the three splanchnic 

 nerves. These are named, the great, the lesser, and the smallest or renal 

 splanchnic. 



