THE CERVICAL SYMPATHETIC TRUNK 343 
only by their course in the sympathetic trunk. One innervates 
the ganglion to which the ramus brings it. The other runs 
through two or more ganglia before it terminates. 
A study of serial sections through the superior cervical ganglion 
of the cat stained with osmie acid is instructive. At the lower 
pole a large bundle of myelinated fibers can be traced into the 
ganglion from the sympathetic trunk. This comes to lie near 
the center of the ganglion and breaks up into smaller bundles. 
Many of the fibers seem to lose their myelin sheaths while still 
within the smaller bundles. At least this seems to be the best 
explanation of the fact that the number of myelinated fibers 
scattered among the ganglion cells is so small. 
When the sympathetic trunk is cut and time allowed for 
degeneration all these bundles of fibers have degenerated. There 
are, however, still present even in the caudal pole of the ganghon 
a very few scattered myelinated fibers which have their cells of 
origin in the ganglion. The number of such fibers increases 
toward the cephalic pole. Here the myelinated and the more 
numerous unmyelinated postganglionic fibers accumulate in 
bundles located especially near the periphery of the ganglion. 
From the pole large branches representing the internal carotid 
nerve are given off. Other smaller branches are given off in 
various places from the ganglion. 
The small number of myelinated fibers which are scattered 
among the ganglion cells in comparison to the number entering 
and leaving the ganglion would indicate that they run consider- 
able distances in the ganglia as unmyelinated fibers. 
In following through a series of sections stained by the pyridine 
silver technique, one sees that the fine axons entering the ganglion 
from the sympathetic trunk are all stained a dark brown. Each 
fiber is surrounded by a thin unstained ring of myelin. This 
central bundle of the ganglion can be seen to break up into smaller 
and smaller bundles of dark fibers and the constituent fibers of 
these smaller bundles can be seen to run into and become a part 
of the intercellular plexus described in the preceding section. 
Following the series toward the cephalic end of the ganglion, 
one sees bundles of axons collecting especially near the periph- 
