596 SYMPATHETIC NERVE. 



rior part of the cavernous plexus ; it accompanies the nasal nerve, or continues 

 forwards as a separate branch. 



The terminal filaments from the carotid and cavernous plexuses are prolonged 

 along the internal carotid, forming plexuses which entwine round the cerebral and 

 ophthalmic arteries ; along the former vessel they may be traced on to the pia mater ; 

 along the latter, into the orbit, where they accompany each of the subdivisions of 

 the vessel, a separate plexus passing with the arteria centralis retinas into the 

 interior of the eyeball. 



CARDIAC NERVES. 



The cardiac nerves are three in number on each side ; superior, middle, and 

 inferior, one being derived from each of the cervical ganglia. 



The Superior Cardiac nerve (nervus superficialis cordis) arises by two or more 

 branches from the superior cervical ganglion, and occasionally receives a filament 

 from the cord of communication between the first and second cervical ganglia. 

 It runs down the neck behind the common carotid artery, lying upon the Longus 

 colli muscle, and crosses in front of the inferior thyroid artery, and the recurrent 

 laryngeal nerve. 



The right superior cardiac nerve, at the root of the neck, passes either in front 

 of or behind the subclaviun artery, and along the arteria innominata, to the back 

 part of the arch of the aorta, to the deep cardiac plexus. This nerve, in its 

 course, is connected with other branches of the sympathetic ; about the middle of 

 the neck it receives filaments from the external laryngeal nerve ; lower down, one 

 or two twigs from the pneumogastric, and, as it enters the thorax, it joins with the 

 recurrent laryngeal. Filaments from this nerve accompany the inferior thyroid 

 artery to the thyroid gland. 



The left superior cardiac nerve runs by the side of the left carotid artery, and 

 in front of the arch of the aorta, to the superficial cardiac plexus; it occasionally 

 passes behind this vessel, and terminates in the deep cardiac ^plexus. 



The Middle Cardiac nerve (nervus cardiacus magnus), the largest of the three, 

 arises from the middle cervical ganglion, or from the interganglionic cord between 

 the middle and inferior ganglia. On the right side, it descends behind the common 

 carotid artery ; and, at the root of the neck, passes either in front of or behind the 

 subclavian artery ; it then descends on the trachea, receives a few filaments from 

 the recurrent laryngeal nerve, and joins the deep cardiac plexus. In the neck, it 

 communicates with the superior cardiac and recurrent laryngeal nerves. On the 

 left side, the middle cardiac nerve enters the chest between the left carotid and 

 subclavian arteries, and joins the left side of the deep cardiac plexus. 



The Inferior Cardiac nerve (nervus cardiacus minor) arises from the inferior 

 cervical or first thoracic ganglion. It passes down behind the subclavian artery, 

 and along the front of the trachea, to join the deep cardiac plexus. It communi- 

 cates freely behind the subclavian artery with the recurrent laryngeal and middle 

 cardiac nerves. 



CARDIAC AND CORONARY PLEXUSES. 



The Great or Deep Cardiac Plexus (yrtexus magnus profundus Scarpa) is 

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

 pulmonary 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 left inferior cardiac branch from the pneumogastric. The branches 

 derived from the great cardiac plexus form the posterior coronary plexus, and 

 part of the anterior coronary plexus ; whilst a few filaments proceed to the pul- 

 monary plexuses, and to the auricles of the heart. 



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



