THE SYMPATHETIC SYSTEM. 215 



there are only three ganglia, but they communicate with 

 all the cervical nerves; and the uppermost ganglion, which is 

 the largest, sends branches upwards into the skull, round 

 the internal carotid artery. Within the skull the chain 

 can be traced, in somewhat irregular fashion, communi- 

 cating with the fifth and other nerves; and two cords pass 

 forwards, one on each side of the septum of the nose, to 

 unite on the palate behind the incisor teeth, and form the 

 superior termination of the chain, at the spot which I once 

 demonstrated, and still hold, to be the arch of the foremost 

 segment of the skull. , 



In the neck, the sympathetic chains give off branches to 

 the heart; and in the chest they send twigs to the lungs. 

 From the thoracic ganglia there likewise descend three pairs 

 of splanchnic nerves, which form a very large plexus in the 

 upper part of the abdomen, the solar plexus. This plexus 

 contains two large semilunar ganglia, and sends branches 

 along the blood-vessels to the stomach, liver, intestines, 

 and other abdominal viscera, and communicates by large 

 branches on the aorta with the hypogastric plexus, 

 which is placed within the pelvis and supplies the viscera 

 there. 



The sympathetic system is especially devoted to the supply 

 of the viscera and blood-vessels, but it is by no means inde- 

 pendent of the cerebro-spinal system; as is proved anatomi- 

 cally by its close connection with the pneumogastric nerves 

 and its communications with the spinal cord, and physiologi- 

 cally by the conveyance of influences through it from the 

 cerebro-spinal axis. That nervous influence is so conveyed 

 is illustrated by many familiar effects of mental conditions 

 on different visceral actions, but still more explicitly by 

 the effects of experiments on the nerves to the blood- 

 vessels. 



158. The vaso-motcr nerves, or nerves to the arterioles, form 

 an important part of the sympathetic system. When in action, 

 they contract the muscular coats of the vessels, and limit the 

 amount of blood to the part supplied by them; and it has 

 been already pointed out (p. 125), that division of the sym- 

 pathetic in the neck causes paralysis, and consequent disten- 

 sion, of the arteries of the head. But division of the spinal 



