CHAP. XXI.] PLEXUSES OF THE SYMPATHETIC. 139 



/ Of the Thoracic and Abdominal Plexuses. So large a portion of 

 i. jthe sympathetic is distributed to viscera in the thorax and abdomen, 

 that it may not improperly be designated as the visceral nerve; 

 for those organs, upon which the great processes which contribute 

 to the nutrition of the body so much depend, derive their nerves 

 mainly from this source, and whatever cerebro-spinal fibres they re- 

 ceive, are distributed to them in intimate association with the 

 proper filaments of the sympathetic. 



The plexuses in the thorax which derive nerves from the sym- 

 pathetic are the pulmonary plexus, and the cardiac plexus. 



The pulmonary plexus is chiefly formed by branches of the vagus, 

 interlacing with each other from opposite sides along the median 

 plane. It occupies two planes, one anterior to the bronchi constitut- 

 ing the anterior pulmonary plexus, the other posterior, which is much 

 the more considerable and lies behind the bronchi. To these, but 

 especially to the latter, nerves pass off from the higher thoracic 

 ganglia. 



The cardiac plexus is almost wholly derived from the sympa- 

 thetic, only a few of its fibres coming from the cardiac branches of 

 the vagi. It is very remarkable that all the nerves which the sym- 

 pathetic contributes to this plexus, are derived from the cervical, 

 and not from the thoracic ganglia. The plexus resulting from the 

 anastomoses of these nerves, occupies an anterior and a posterior 

 plane ; the former passing in front of the great arteries, and follow- 

 ing the course of the anterior coronary artery, in the anterior groove 

 of the heart. The plexus entwines round this artery and its ramifica- 

 tions, and its fibres are doubtless conducted by them to the muscular 

 fibres of the heart. The posterior plexus follows the course of the 

 right coronary artery, and of its branches, which lies in the posterior 

 fissure of the heart. A plexus of fibres, occupying a position inter- 

 mediate to these plexuses, lies behind the arch of the aorta, above the 

 right pulmonary, and sends a considerable plexus of nerves to the 

 auricles. This plexus was described by Haller, as the great cardiac 

 plexus. 



Several small ganglia, or gangliolaj are found in connexion with 

 the nerves of the heart. Wrisberg described one just above the 

 arch of the aorta, at the junction of anastomosing fibres from the 

 superior cardiac nerves. A ganglion is also sometimes found in the 

 plexus in front of the auricles, and Remak describes and figures 

 several small ganglia upon the subdivisions of the anterior and pos- 

 terior cardiac plexuses, and in the muscular substance of the heart.* 

 * MiiUer's Archiv., 1844. 



