CHAP. XXI.] THE SPLANCHNIC NERVES. 137 



superior cervical ganglion. It is connected with the fifth, sixth, 

 and seventh cervical nerves, and sometimes with the first dorsal. 



The arterial and visceral branches of this ganglion are, 1. A 

 nerve which accompanies the vertebral artery into the canal formed 

 by the transverse processes of the cervical vertebrae. This nerve 

 forms a plexus round the vertebral artery and communicates with 

 branches of the five lowest cervical nerves. There is no satisfac- 

 tory evidence that this nerve passes up to the arteries of the brain. 

 It seems chiefly a nerve to the vertebral artery, but doubtless also 

 contains fibres from the cervical spinal nerves, which probably have 

 a different destination. 2. The second branch of this ganglion is 

 the third or inferior cardiac nerve which passes down, frequently 

 in company with the middle cardiac nerve, to the plexus on the 

 heart. 3. Branches which encircle the subclavian artery, in the 

 first part of its course. 



It is worthy of note that the most important visceral branches 

 of the cervical portion of the sympathetic are destined to an organ, 

 the heart, which is situated in the thorax at a considerable distance 

 from their source. 



3. The Thoracic Portion of the Sympathetic consists of a series 

 of ganglia, corresponding, or nearly so, in number to that of the 

 vertebrae; the ganglia lie upon the heads of the ribs, and are mostly 

 small in size, and triangular in form. The first thoracic ganglion 

 is often fused with the last cervical. 



Besides the branches of communication with the spinal nerves, 

 there are arterial branches which pass to the aorta, and there are 

 also branches which pass into the pulmonary plexus. 



But the most remarkable nerves which proceed from these gan- 

 glia, are the greater and the lesser splanchnic nerves. 



The great splanchnic nerve arises by separate roots probably 

 from all the thoracic ganglia, more obviously from the fifth, sixth, 

 seventh, eighth, and ninth; these roots unite to form a round 

 cord, as large, if not larger, than the trunk of the sympathetic. 

 This nerve passes alongside of the bodies of the vertebrae obliquely 

 downwards and forwards, enters the abdomen by piercing the 

 diaphragm, and ends in a large and complex ganglion placed by 

 the side, and in front of the aorta, close to the origin of the cseliac 

 artery; this is the great semilunar ganglion.* 



* The composition of this nerve deserves particular attention as illustrating 

 the compound nature of the ramifications of the sympathetic. It may be regard- 

 ed as the aggregate of a series of visceral nerves proceeding from the intercostal 

 nerves, each of which, as it passes over the sympathetic ganglion immediately 



