THORACIC TRUNCUS SYMPATHICUS 433 
far presented would not exclude the possibility that these unmye- 
linated fibers might be preganglionic fibers that had lost their 
myelin sheaths, but in the paper which follows we will present 
evidence to show that they are afferent fibers and arise from the 
cells in the spinal ganglia. 
Since there are few large myelinated and unmyelinated fibers 
Fig.8 Apart of asection through the tenth thoracic internodal segment in the 
cat. Pyridine silver. X 425. 
in the sympathetic trunk below the stellate ganglion and prac- 
tically none in the cervical part of the trunk, we must conclude 
that the sensory fibers which reach the stellate ganglion by way 
of the first three white rami run out again through the branches 
of the stellate or the inferior cervical ganglion. These branches 
have been studied in only one cat. The cardiac branch of the 
stellate ganglion, while consisting chiefly of unmyelinated fibers, 
contained a somewhat larger number of myelinated fibers than 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 29, No. 4 
