SACRAL SYMPATHETIC TRUNK OF CAT 99 
division of the seventh lumbar internodal segments, since pre- 
ganglionic fibers are absent in the gray rami (Langley, 796). 
The most probable explanation for the presence of these fibers 
appears to be that they are afferent (dorsal root) fibers which 
enter the trunks by way of the gray rami. Such a large number 
of dorsal root fibers entering the trunks by this route was not 
expected, and in order to make certain as to the source of these 
fibers the second series of experiments was carried out. 
In the first cat operated for this experiment both trunks were 
cut between the seventh lumbar and the first sacral ganglion. 
A week later the lamina of the sacrum and the sixth and seventh 
lumbar vertebrae were resected and the entire cauda equina 
and conus medullaris removed. White ramus fibers descending 
in the trunk were eliminated by the first operation, while the 
second operation removed the source of any dorsal root fibers 
which might reach the trunk through the sacral gray rami. The 
cat was killed thirty days after the operation. On dissection 
the trunks and rami were found to be much more reduced in 
diameter than was usual in the singly operated specimens. The 
trunks were stained in osmic acid and serial sections cut from 
the first sacral to the third coccygeal ganglion. <A section of 
lumbar trunk was run as a control and short pieces of the sacral 
nerves were stained and sectioned in order to check up on the 
degeneration of dorsal and anterior root fibers in the spinal 
nerves. ‘These sections showed practically complete degenera- 
tion of all medullated fibers. 
In a section through the first sacral ganglion there were found 
only five small medullated fibers ranging from about 1.2 to 2u 
in diameter. They occupy a small part of a fairly large fascicle, 
the other medullated fibers of which have undergone degenera- 
tion. A few sections caudad this fascicle separates from the 
trunk to form a gray ramus. In sections through the internodal 
segment just caudad to the ganglion no medullated fibers could 
be found, although it was expected that a few of the same type 
as found in the ramus would be present. The conditions found 
in the rest of the trunk may be summed up briefly in the state- 
ment that all large and intermediate fibers as well as the majority 
