70 DISSECTION OF THE NECK 



corresponding spinal nerve. These branches of com- 

 munication are known as the rami commiinicaiites. 



In the posterior portion of the thorax, just after 

 c:ivino: off a ramus communicans to the 12th or the 

 13th thoracic spinal nerve, the sympathetic sends off a 

 large branch to the inner side, known as the splanchnic 

 nerve. This nerve passes through the diaphragm and 

 (in the dog) ends in a ganglionic enlargement, the 

 splanchnic ganglion. From this ganglion small 

 branches can be traced inward and forward, ending in 

 a larger nerve-mass, the cceliac ganglion, which lies just 

 posterior to the coeliac axis and on the ventral aspect 

 of the aorta. There is a similar arrangement on the 

 other side, the two coeliac ganglia being connected 

 with each other by cross-branches and sending very 

 numerous fine branches to the surrounding abdominal 

 organs, which form what is called the solar plcxns. 

 The solar plexus, as before mentioned, is connected 

 with the terminal plexuses of the vagi. 



After giving off the splanchnic the sympathetic 

 may have one more ganglion in the thorax, from which 

 a ramus communicans is given to the 13th thoracic 

 spinal nerve, and a small branch, \\\t small splanchnic, 

 which joins the splanchnic ganglion. It then passes 

 through the diaphragm and continues as the abdomi- 

 nal sympathetic, which also has ganglionic enlargements 

 as in the thorax. From these ganglia branches arise 

 which form plexuses, similar to the solar plexus, for 

 the abdominal and pelvic organs. The two sympa- 

 thetic trunks finally unite at the posterior end of the 

 sacrum in an unpaired ganglion lying in the mid-line. 



19. The Brachial Plexus in the dog is formed from 

 the 6th, 7th and 8th cervical spinal nerves and the 

 I St thoracic spinal nerve, and usually receives a small 



