DISSECTION OF THE BACK AND THORAX. 117 



right is reflected round a comparatively small artery, while the left is 

 reflected round the great aorta The right recurrent nerve is not impli- 

 cated in "roaring." 



3. Cardiac Bramhes, 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 Roots of the Brachial Plexus. These do not differ from 

 those of the left side (page 109). 



The Sympathetic Nerve. 



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

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

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

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

 it to the inferior cervical ganglion. It communicates with the vagus 

 and recuiTent nerves, and gives off the cardiac nerve accompanying the 

 vagus beneath the axillary artery. 



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

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

 cal 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 back beneath the arch of the axillary artery. Reach- 

 ing the lower face of the trachea, it vmites 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. 



[' ' On the right side we reckon two principal cardiac nerves and four secondary filaments. 

 The first cardiac nerve is a long branch which takes origin at the level of the middle cer- 

 vical ganglion. It is formed by fibres from the sympathetic and by a fasciculus furnished 

 by the right pneumogastric, at the entrance to the chest ; it receives probably also some 

 medullary fibres through the intermediation of a branch of communication thrown 

 between the middle ganglion and the inferior ganglion. This nerve is reinforced by two 

 filaments which proceed from the inferior cervical ganglion, and sometimes from the 

 second middle ganglion, of which one, the posterior, is reinforced in the same way by a 

 left sympathetic filament which gains its destination in passing alongside of the recurrent 



