CARDIAC PLEXUS. 537 



origin of the arteria innominata, and extends downwards to the 

 bifurcation of the pulmonary artery. 



As has been ah-eady mentioned, it is principally composed of 

 branches from the middle cardiac nerve of the right side, and 

 the inferior cardiac nerve of the left ; but it receives branches 

 from the superior cardiac of the left, and sometimes of the right 

 side. Some fibres of the inferior cardiac of the right are also 

 united to it. 



Many branches proceed from this plexus. 



A sniall number pass upon the aorta, and seem to enter into 

 its texture.* 



Some of them also combine with the ramifications of the Par 

 Vagiim in the anterior pulmonary plexus. 



The majority proceed to the basis of the heart, near the origin 

 of the pulmonary artery and the aorta, and constitute the 'proper 

 nerves of that organ. They accompany the coronary arteries, 

 and are so arranged around them that, by some anatomists, they 

 have been said to form plexuses, which have been denominated 

 Coronary. 



The Sympathetic Nerve, as has been stated above, proceeds 

 from the ganglion, called the Lower Cervical, or the First Tho- 

 racic, before the neck of the first rib. It continues to descend, 

 in the same direction, along the spine, exterior to the pleura, to 

 the inferior part of the thorax. Near the head of each rib it 

 forms a ganglion, which unites with the intercostal nerve behind 

 it, by two branches, and thus forms an indirect communication 

 with the medulla spinalis. 



From several of the uppermost of these ganglions small twigs 

 proceed to the pulmonary plexus, and also to the great trunk of 

 the aorta, below the curve forming a species of net-work, or 

 plexus upon it. 



From the ganglions near the heads of the fifth and sixth 

 ribs, and from four or five of the ganglions which succeed 

 them, small nerves arise, which proceed downwards on the 



* It has been asserted that some of the anatomists of Paris have traced these 

 nerves on the aorta, to a great distance from the heart. 



