ANALYSIS OF THE SYMPATHETIC TRUNK 4595 
are more closely grouped together in figure 10. Since this 
partially degenerated fascicle could be traced to the white rami 
of the ninth and tenth thoracic nerves, the roots of which had 
been cut proximal to the spinal ganglia, it is clear that the normal 
fibers remaining in this fascicle were not preganglionic autonomic 
fibers. They must either have been afferent, with their cells 
of origin in the spinal ganglia, or they must have been directed 
from the sympathetic ganglia toward the spinal ganglia or spinal 
cord. The complete degeneration of the greater part of the trunk 
at the level of the twelfth thoracic internodal segment after sec- 
tion of the trunk below the ninth thoracic ganglion in Cat XII, 
as illustrated in figure 5, shows that these fibers do not take origin 
from the sympathetic gangha. 
The partially degenerated fascicle from the ninth and tenth 
white rami made no contribution to the greater splanchnic nerve, 
but was continued along the trunk into the lesser splanchnic. 
Osmiec acid and silver preparations of the greater splanchnic 
showed that this nerve was entirely normal, while similar prepa- 
rations of the lesser splanchnic showed that it had the same 
structure as the partially degenerated fascicle in the trunk. 
SUMMARY 
Section of the thoracic spinal nerve roots proximal to the spinal 
ganglia results in a degeneration of all of the preganglionic auto- 
nomic fibers in the corresponding white rami, but leaves the 
afferent fibers intact. The white rami studied were the ninth, 
tenth, and eleventh. The fibers from these partially degenerated 
rami could be traced caudad in the trunk, those from each ramus 
forming a well-defined fascicle. It is this arrangement which 
makes it possible to trace the fibers of the splanchnic nerve by 
dissection to the white rami as high as the sixth. The afferent 
fibers, which alone remained in these partially degenerated rami 
and the corresponding fascicles of the trunk, included myelinated 
fibers of all sizes and many that were unmyelinated. They 
took origin from the cells of the spinal ganglia. In one case after 
section of the tenth thoracic nerve distal to the spinal ganglion 
we found a half-dozen normal myelinated fibers in the corre- 
