THORACIC TRUNCUS SYMPATHICUS 435 
Usually in pyridine silver preparations it is possible to see that 
there are somewhat larger accumulations of unmyelinated fibers 
near the periphery or directly under the perineurium. These 
do not constitute well-defined fascicles such as one would expect 
to find if any large number of postganglionic fibers were present. 
They are probably of the same nature as those scattered through 
the nerve. 
In two out of ten normal greater splanchnic nerves examined 
we found evidence of postganglionic fibers in the form of a well- 
defined and fairly good-sized fascicle composed chiefly of un- 
myelinated fibers. Preparations of the first lumbar segment of 
the sympathetic trunk and the greater splanchnic nerve taken 
xm Ww LG. 
G 
I.L.Gang. 
ILL Gano. 
ie NM splaneh.min. 
Mspla nch.ma}. 
Fig.9 Diagram of the upper lumbar portion of the sympathetic trunk of a cat 
in which there was an accessory ganglion at the origin of the greater splanchnic 
nerve. XIII. W., white ramus to the XIII thoracic nerve; I. G., gray ramus 
to the I lumbar nerve; I. W., white ramus of the I lumbar nerve; II. G., gray 
ramus to the II lumbar nerve. 
from Cat 8 were especially instructive. Figure 9 shows that in 
the first lumbar segment of the trunk there was a ganglion, not 
connected with the spinal nerves by rami, located at the point of 
origin of the greater splanchnic nerve. The entire portion of the 
sympathetic trunk shown in the figure was cut in serial sections. 
A study of these sections shows that no branches, even of micro- 
scopic size, are given off from the trunk at the level of this gan- 
glion except the splanchnic nerve. As this nerve leaves the trunk 
it carries with it a rather large bundle of peripherally placed 
unmyelinated fibers which closely resembles the crescentic area 
described in the trunk. It seems probable that this unusual 
bundle of fibers takes origin from the cells in this aberrant 
ganglion. 
The observations so far recorded lead one to conclude that the 
greater splanchnic nerve is composed chiefly of preganglionic 
