488 THORACIC GANGLIA. 



supplies the anterior aspect of the heart, distributing numerous fila- 

 ments with the left coronary artery, which form the anterior coronary 

 plexus. 



The Posterior cardiac plexus is formed "by numerous branches from 

 the great cardiac plexus, and is situated upon the posterior part of the 

 ascending aorta, near its origin. It divides into two sets of branches: 

 one set accompanying the right coronary artery in the auriculo-ventri- 

 cular sulcus ; the other set joining the artery on the posterior aspect 

 of the heart. They both together constitute the posterior coronary 



The great cardiac plexus likewise gives branches to the auricles of 

 th'e heart, and others to assist in forming the anterior and posterior 

 pulmonary plexuses. 



THORACIC GANGLIA. 



The Tfioracic ganglia are twelve in number on each side. They 

 are flattened and triangular, or irregular in form, and present the 

 peculiar grey colour and pearly lustre of the other sympathetic 

 ganglia ; they rest upon the heads of the ribs, and are covered in by 

 the pleura costalis. The two first ganglia and the last are usually the 

 largest. 



Their branches are superior, inferior, external, and internal. 



The superior and inferior are prolongations of the substance of the 

 ganglia rather than branches ; the former to communicate with the 

 ganglion above, the latter with that below. 



The external branches, two or three in number, communicate with 

 both roots of each of the spinal nerves. 



The internal branches of the five upper ganglia are pulmonary to join 

 the pulmonary plexuses ; cesophageal to the cesophageal plexus and aortic 

 to the thoracic aorta and its branches ; the first thoracic ganglion more- 

 over sends branches to the cardiac plexuses. The branches of the 

 lower ganglia are aortic, and several large cords which unite to form 

 the two splanchnic nerves. 



The Great splanchnic nerve arises from the sixth dorsal ganglion, 

 and receives branches from the seventh, eighth, ninth, and tenth, 

 which augment it to a nerve of considerable size. It descends in 

 front of the vertebral column, within the posterior mediastinum, pierces 

 the diaphragm immediately to the outer side of each crus, and termi- 

 nates in the semilunar ganglion. 



The Lesser splanchnic nerve (renal) is formed by filaments from the 

 tenth, eleventh, and sometimes from the twelfth dorsal ganglion. It 

 pierces the diaphragm, and descends to join the renal plexus, 



The Semilunar ganglion is a large, irregular, gangliform body, 

 pierced by numerous openings, and appearing like the aggregation of 

 a number of smaller ganglia, having spaces between them. It is 

 situated by the side of the cceliac axis, and communicates with the 

 ganglion of the opposite side, both above and below that trunk, so as 



