ACCESSOEY NEEVE. 791 



is placed behind the arch ,of the aorta, on the sides of the trachea, just above its 

 bifurcation. It consists of two lateral parts, joined together by numerous com- 

 munications around the termination of the trachea. The two portions of the plexus 

 are different in their constitution and distribution. The right half of the plexus 

 is joined by both the cervical and thoracic branches of the right vagus and by the 

 branches of the right recurrent nerve, as well as by branches from the superior, 

 middle, and inferior cervical ganglia of the sympathetic. The left half of the plexus 

 is joined by the superior cervical cardiac branch of the left vagus, by branches from 

 the left recurrent nerve, and by branches from the middle and inferior cervical 

 ganglia of the left sympathetic ; it also receives a contribution from the superficial 

 cardiac plexus. 



The deep cardiac plexus is distributed to the heart and lungs. The right 

 half of the plexus for the most part constitutes the anterior coronary plexus, 

 reaching the heart alongside the ascending aorta, and is distributed to the heart 

 substance in the course of the right coronary artery. It is reinforced by fibres 

 from the superficial cardiac plexus, which reach the heart along the pulmonary 

 artery. Fibres from the right half of the deep cardiac plexus pass also to join 

 the posterior coronary plexus, and others extend laterally to join the anterior 

 pulmonary plexus of the right side. 



The left half of the deep cardiac plexus, reinforced by fibres from the superficial 

 cardiac plexus, is distributed to the heart in the form of the posterior coronary 

 plexus, which is joined by a few fibres behind the pulmonary artery from the right 

 half of the plexus, and supplies the heart substance in the course of the left coronary 

 artery. The left half of the plexus contributes also to the left anterior pulmonary 

 plexus by fibres which extend laterally to the root of the lung along the left 

 branch of the pulmonary artery. 



Plexus Pulmonales (Pulmonary Plexuses). As already stated, the vagus 

 nerve on each side, on reaching the back of the root of the lung, breaks up 

 into numerous plexiform branches for the formation of the posterior pulmonary 

 plexus. From each nerve a few fibres pass to the front of the root of the lung, 

 above its upper border, to form the much smaller anterior pulmonary plexus. 



Plexus Pulmonalis Anterior. The anterior pulmonary plexus on each side 

 is joined by a few fibres from the corresponding part of the deep cardiac plexus, 

 and on the left side from the superficial cardiac plexus as well. It surrounds and 

 supplies the constituents of the root of the lung anteriorly. 



Plexus Pulmonalis Posterior. The posterior pulmonary plexus, placed 

 behind the root of the lung, is formed by the greater part of the vagus nerve, 

 reinforced by fine branches from the second, third, and fourth thoracic ganglia of 

 :he sympathetic. Numerous branches proceed from it in a plexiform manner along 

 :he bronchi and vessels into the substance of the lung. 



Plexus CEsophageus Anterior et Posterior (CEsophageal Plexus). The 

 esophagus in the thorax is supplied by the vagus nerve both in the superior and 

 Dosterior mediastina. In the superior mediastinum it receives branches from the 

 /agus nerve on the right side, and from its recurrent branch on the left side. 



In the posterior mediastinum the gullet is surrounded by the cesophageal plexus, 

 brmed from the trunks of the vagi nerves emerging from the posterior pulmonary 

 )lexuses, which form a large plexus surrounding the gullet. This part of the 

 esophagus also receives fibres from the greater splanchnic nerve and ganglion. 

 From the oesophageal plexus branches supply the muscular wall and mucous 

 nembrane of the oesophagus. 



Pericardiac branches are also supplied from the plexus to the posterior surface 

 )f the pericardium. 



NERVUS ACCESSORIUS. 



The eleventh or accessory nerve (O.T. spinal accessory) consists of two 

 ssentially separate parts, different both in origin and in distribution. One 

 portion is accessory to the vagus nerve, and arises, in series with the fila of that 

 lerve, from the side of the medulla oblongata. The other, spinal portion, arises from 





