7O DISSECTION OF THE NECK 
corresponding spinal nerve. These branches of com- 
munication are known as the ram communicantes. 
In the posterior portion of the thorax, just after 
civing 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 sAlanchuzc 
nerve. ‘\his 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 celzac 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 plexus. 
The solar plexus, as before mentioned, is connected 
with the terminal plexuses of the vag. 
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, the sal 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 
Ist thoracic spinal nerve, and usually receives a small 
