482 NERVOUS SYSTEM. 



anastomoses with each other, to form a single chord, the Infe- 

 rior Cardiac Nerve, which goes, on the right side, along the ar- 

 teria innominata, to be blended with the cardiac plexus. On 

 the left side, it is not so distinct, but is blended with the mid- 

 dle cardiac nerve, and forms its inferior root. 



Of the Cardiac Plexus of the Sympathetic. 

 



The Cardiac Plexus (Plexus Cardiacus) is situated between 

 the arch of the aorta, and the lower part of the trachea and the 

 bronchia, and extends from the division of the pulmonary ar- 

 tery to the commencement of the arteria innominata. It is 

 formed, almost wholly, from the branches sent by the three 

 cervical ganglions of the symphathetic of each side, and princi- 

 pally from that of the middle one, or the middle cardiac nerve. 

 The filaments which come from the recurrent nerve and the 

 par vagum are blended into the cardiac plexus in such a man- 

 ner that they cannot be traced separately to the heart. It is 

 worthy of remark, that the three cardiac nerves of the right 

 side are more constantly found than the same number on the 

 left, in consequence of the lower one of the latter soon merging 

 itself, after its origin into the middle cardiac nerve of that 

 side. 



The cardiac plexus is formed by the common assemblage of 

 the nerves from the two sides of the neck, and is therefore sin- 

 gle. From this plexus arise all the nerves which go to the 

 heart, so that in tracing them the distinction between right and 

 left is confounded. Scarpa has pointed out, in this circumstance, 

 an analogy between them and the nerves which supply the ab- 

 dominal viscera. 



The cardiac plexus is distinguished by the softness of its tex- 

 ture. For the purpose of description, its branches may be di- 

 vided into Anterior, Posterior, and Inferior. 



The Anterior Branches are but few. They are found on the 

 front of the arch of the aorta. One of them crosses it on the 

 right side of the arteria innominata; others cross it from the 

 foot of the left carotid and subclaviau, downwards. In both 



