332 DISSECTION OF THE THORAX. 



and close above the pulmonary artery, and is to be drawn over to the left 

 side : next the upper cava is to be divided above the entrance of the vena 

 azygos, and its lower part is to be thrown down. By the removal of some 

 fibrous and tatty tissues and lymphatic glands, the right part of the plexus, 

 in which the nerves of the right side are united, will be seen in front of the 

 trachea, above the right branch of the pulmonary artery. The offsets to 

 the heart should be followed downwards on the trunk of the pulmonary 

 artery ; and those to the lung should be traced along the right branch of 

 that vessel. 



To lay bare the part of the plexus into which the nerves of the left side 

 of the body enter, the arch is to be cut through a second time, to the 

 right of and close to the junction of the ligamentum arteriosum with it ; 

 and the transverse part of the arch is to be turned upwards with the great 

 vessels attached. The lymphatic glands and the areolar and fatty tissue 

 being cleared away from the plexus as on the opposite side, the offsets to 

 the posterior coronary plexus of the heart are to be cleaned. 



Deep cardiac plexus. This large centre is situate between the trachea 

 and the arch of the aorta, above the branches of the pulmonary artery. 

 In it are united the cardiac nerves of the sympathetic of both sides of the 

 neck, except the highest nerve of the left side : and the cardiac branches 

 of the vagus in the neck and chest, with the exception of the lowest 

 cervical branch of the left side. From it nerves are furnished to the heart 

 and lungs. 



The several nerves entering the plexus are not intermingled in a plexi- 

 form mass in front of the trachea ; but those of the right side unite 

 together on the right of the air tube, and those of the left have a like 

 junction on their side. 



The right part of the plexus is placed above the right branch of the 

 pulmonary artery, and receives the nerves of the right side, viz., the car- 

 diac nerves of the sympathetic in the neck ; the cardiac branches of the 

 trunk of the vagus, in both the neck and chest ; and the cardiac offsets of 

 the recurrent branch. 



The branches of this half of the plexus are distributed mostly to the 

 right side of the heart, and pass downwards before and behind the right 

 branch of the pulmonary artery : those in front running on the trunk of 

 the pulmonary artery to end in the anterior coronary plexus (p. 315) ; and 

 the nerves behind supply the right auricle of the heart. Offsets are sent 

 laterally on the branch of the artery to the root of the lung. 



The left half of the plexus lies close to the ligamentum arteriosum, and 

 rather on the left of the trachea. In it are collected the cardiac nerves of 

 the sympathetic ganglia of the left side of the neck, except the highest ; 

 and numerous and large branches of the left recurrent nerve of the vagus. 



Nerves descend from it to the heart around the left branch and trunk of 

 the pulmonary artery, and after supplying branches to the left auricle, ter- 

 minate in the posterior coronary plexus (p. 31f>). A considerable offset is 

 directed forwards by the side of the ligamentum ductiis arteriosi to the 

 superficial cardiac plexus ; and some nerves reach the left anterior pulmo- 

 nary plexus by passing along the branch of the pulmonary artery. 



Termination of the cardiac branches of the sympathetic nerve of the 

 neck (p. 117). 



On the right side there are usually only two cardiac nerves entering the 

 thorax, for the highest nerve is blended commonly with one of the others. 

 The middle and inferior nerves pass beneath the subclavian artery to the 



