DISSECTION OF THE BACK AND THORAX. 119 



vib, while the left has its origin at the base of the heart. Moreover, the 

 right is reflected round a comparatively small arterj', while the left is 

 reflected round the great aorta. The right recurrent nerve is not 

 implicated in "roaring." 



3. Cardiac Branches, variable in number, pass downwards and back- 

 wards to reach the lower face of the trachea, whence, after anastomosing 

 intricately with the sympathetic cardiac nerves, they pass on to the 

 right auricle. 



4. Pulmonary Branches as on the left side. 



Dorsal Eoots of the Brachial Plexus. These do not differ from 

 those of the left side (page 112). 



The Sympathetic Nerve. 



The Middle Cervical Ganglion. — Tliis resembles that of the left side. 

 It is placed on the trachea, internal to the insertion of tlie scalenus 

 muscle into the 1st rib. It receives the cervical cord of the sympathetic 

 in front, and behind it is prolonged by a short cord connecting it to the 

 inferior cervical ganglion. It communicates with the vagus and re- 

 current nerves, and gives off the cardiac nerve accompanying the vagus 

 beneath the axillary artery. 



The Inferior Cervical Ganglion is situated on the longus colli, at the 

 upper edge of the trachea, and between the vertebral and superior 

 cervical arteries. It receives the vertebral nerve and branches from 

 the inferior primary divisions of the 8th cervical and first two dorsal 

 nerves, and is continued into the dorsal cord of the sympathetic as on 

 the left side. It emits a cardiac nerve. 



Cardiac Nerves of the right side. — (1) The middle cervical ganglion 

 detaches a considerable cardiac nerve which accompanies the right 

 vagus in passing bacli beneath the arch of the axillary artery. Reach- 

 ing the lower face of the trachea, it unites with one of the cardiac 

 nerves of the left side, and is reflected behind the common aorta to be 

 distributed to the left side of the heart, as already described. This 

 nerve emits a branch to unite with another cardiac nerve of the left 

 side — that which follows the right coronary artery. (2) The inferior 

 cervical ganglion gives origin to a cardiac nerve, smaller than the 

 preceding, which it joins after giving fibres to the right vagus and 

 recurrent. (3) The cardiac branches of the right vagus have already 

 been seen. 



The Right Dorsal Cord of the Sympathetic does not differ materially 

 from the left. 



The Posterior Aorta is here seen in a large part of its course, but it 

 has already been fully described in connection with the left side. It 

 detaches to this side thirteen intercostals, exactly similar to those of 



the left. 



The Broncho-CEsophageal Artery. This artery arises from the 



