THORACIC GANGLIA. 597 



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 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 pkxus 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 pneu- 

 mogastric, and by 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, and 

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

 plexus. 



The Posterior Coronary plexus is formed chiefly by filaments 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 pkxus is prolonged 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 demonstrated with- 

 out 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. 



THOKACIC 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 vertebra. The ganglia are small in size, and of a 

 grayish color. The first, larger than the rest, is of an elongated form, and usually 

 blended with the last cervical. They are connected together by cord-like pro- 

 longations from their substance. 



The external branches from each ganglion, usually two in number, communicate 

 with each of the dorsal spinal nerves. 



The internal branches from the six upper ganglia are very small, and distribute 

 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. 



The Great Splanchnic nerve is of a white color, firm in texture, and bears a 

 marked contrast to the ganglionic nerves. It is formed by branches from the 

 thoracic ganglia between the sixth and tenth, receiving filaments (according to 



