THORACIC TRUNCUS SYMPATHICUS 409 
The ganglion stellatum lies ventral to the first intercostal space 
and the angle of the second rib. It receives the gray and white 
rami from the first three thoracic nerves and sometimes from the 
fourth also. In addition it gives off a gray nerve, the ramus 
vertebralis, which follows the vertebral artery and gives off 
branches to the lower cervical nerves. According to Langley 
(94), it can be traced in the cat as high as the third cervical 
nerve. The gray ramus to the eighth cervical nerve may run 
by itself. From its connection with the spinal nerves it is obvi- 
ous that the stellate ganglion represents a fusion of elements 
which in man are found in the middle and inferior cervical and 
the first three (and sometimes four) thoracic ganglia. Beginning 
with the fourth or fifth thoracic segment, the ganglia are more 
regularly arranged. But sometimes a ganglion from which a 
gray ramus arises may be very small, and occasionally scattered 
ganglion cells or even fairly large ganglionic masses are found 
in the internodal segments. 
Rami communicantes. While there is a gray ramus for each 
spinal nerve the white rami have a more limited distribution. 
Gaskell (86) thought that in the dog they were associated 
with the second thoracic to the second lumbar nerves only. 
But Langley (’92 a) has shown that in the dog, cat, and rabbit, 
white rami run from the first thoracic to the fourth lumbar nerves 
inclusive. Miller (09) has shown that in man, contrary to the 
usual statement, the third and fourth lumbar nerves possess white 
rami. The rami communicantes of the first two thoracic nerves 
in the cat run directly to the stellate ganglion, those of the third 
usually join the trunk a short distance below and ascend in a 
common sheath with the trunk to reach this ganglion. The 
gray and white rami of the upper two or three thoracic nerves 
are commonly fused together, forming one mixed ramus for each 
of these nerves. From the fourth to the eighth spinal nerve the 
Fig. 1 Diagram of the thoracic portion of the sympathetic trunk in the eat. 
Any branches which may run to the pulmonary or aortic plexuses are usually so 
fine as to escape notice in a careful dissection carried out with the aid of binocular 
lenses of X 2 magnification. In one case we found a branch from the sixth 
thoracic ganglion to the pulmonary plexus and one from the tenth to the aorta. 
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